Optical fiber laser device

ABSTRACT

An optical fiber laser device generates laser light by using an optical amplifying fiber as an amplification medium in a laser oscillator and includes: an optical outputting fiber configured to emit laser light to an outside; a return-light-attenuating portion configured to perform an attenuation process to return light propagating through at least the optical outputting fiber in a reverse direction of the laser light; a thermal conversion unit provided at the return-light-attenuating portion and configured to convert the return light into heat; a temperature-monitoring device configured to measure an increase in a temperature, of the return-light-attenuating portion, caused by the heat converted by the thermal conversion unit; and a control unit configured to decrease or stop an output of the laser light when the temperature measured by the temperature-monitoring device becomes a predetermined threshold temperature or higher.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of International Application No.PCT/JP2015/069342, filed on Jul. 3, 2015, which claims the benefit ofpriority from Japanese Patent Application No. 2014-139047 filed on Jul.4, 2014, and Japanese Patent Application No. 2015-096100 filed on May 8,2015, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to an optical fiber laser device.

Optical fiber laser devices using an optical fiber for an opticalamplifying portion of a laser oscillator or an optical amplifier havebeen used in various fields such as laser-processing or the like.

In such optical fiber laser devices, a so-called return light problemoccurs sometimes that a reflected laser light is coupled to a core of anoptical fiber inside the optical fiber laser device (for example, seeWO2014/014068 or WO2012/073952). When the optical fiber laser device isused as a laser-processing apparatus, this return light is generatedbecause, for example, laser light irradiated to a workpiece is reflectedby the workpiece. This return light is considered to be generated by areflection as well at various locations such as a crack in the opticalfiber used in the optical fiber laser device, a defect at an opticalconnection portion.

This return light may be propagated in the optical fiber in the opticalfiber laser device in a reverse direction of laser light output by thelaser oscillator, and it may damage composing parts of the optical fiberlaser device sometimes. A composing part of the optical fiber laserdevice which may be affected and damaged by the return light may be, forexample, a light emission element that emits a guide light pointing aposition where laser light for laser machining is emitted. Even if acomposing part is not provided to an end portion where the return lightreaches, it may be a problem from a view point of securing safety ifhigh power return light is emitted from the end portion.

However, the above-described return light may be unforeseeablequalitatively and quantitatively sometimes. For example, the returnlight may be amplified while propagating through an oscillator or anamplifier in the optical fiber laser device. A stimulated Ramanscattered light whose wavelength is longer than that of laser lightoscillated by the laser oscillator may be generated sometimes in aprocess of propagation through the optical fiber in the optical fiberlaser device. Therefore, when adopting a countermeasure for return lightwith specific power and specific wavelength, the return light could notbe attenuated appropriately, and thus, composing parts of the opticalfiber laser device may be damaged.

SUMMARY

It is an object of the present disclosure to at least partially solvethe problems in the conventional technology.

According to one aspect of the present disclosure, there is provided anoptical fiber laser device for generating laser light by using anoptical amplifying fiber as an amplification medium in a laseroscillator, the optical fiber laser device including: an opticaloutputting fiber configured to emit laser light to an outside; areturn-light-attenuating portion configured to attenuate return lightpropagating through at least the optical outputting fiber in a reversedirection of the laser light; a thermal conversion unit provided at thereturn-light-attenuating portion and configured to convert the returnlight into heat; a temperature-monitoring device configured to measurean increase in a temperature, of the return-light-attenuating portion,caused by the heat converted by the thermal conversion unit; and acontrol unit configured to decrease or stop an output of the laser lightwhen the temperature measured by the temperature-monitoring devicebecomes a predetermined threshold temperature or higher.

According to another aspect of the present disclosure, there is providedan optical fiber laser device for generating laser light by using anoptical amplifying fiber as an amplification medium in a laseroscillator, the optical fiber laser device including: an opticaloutputting fiber configured to output laser light to an outside in aforward direction; and a return-light-attenuating portion formed of anoptical attenuating fiber coiled for a plurality of rounds, wherein abending loss in return light is greater than a bending loss in visiblelight, the return light being infrared light propagating through theoptical outputting fiber in a reverse direction of the laser light.

According to further aspect of the present disclosure, there is providedan optical fiber laser device for generating laser light by using anoptical amplifying fiber as an amplification medium in a laseroscillator, the optical fiber laser device including: an opticaloutputting fiber configured to output the laser light to an outside in aforward direction; and a return-light-attenuating portion configured toattenuate an optical intensity of return light including infrared lightpropagating a core of the optical outputting fiber in a reversedirection and emit the attenuated return light from an end portion on anopposite side to the optical outputting fiber, wherein thereturn-light-attenuating portion includes: a return light propagationloss portion made of a medium, the medium giving a loss to the returnlight continuously in a direction of propagation of the return light;and a thermal conversion portion configured to convert light generatedby the loss into heat, a major portion of the return light is attenuatedand subjected to thermal conversion at the return light propagation lossportion, and only light, of which intensity is minute, remaining afterbeing attenuated is output from an end portion of the return lightpropagation loss portion.

The above and other objects, features, advantages and technical andindustrial significance of this disclosure will be better understood byreading the following detailed description of presently preferredembodiments of the disclosure, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic configuration of an optical fiber laserdevice according to a first embodiment of the present disclosure;

FIG. 2 is a graph illustrating an example of determination conducted ata control unit using a threshold relevant to temperature;

FIG. 3 is a graph illustrating an example of determination conducted atthe control unit using the threshold relevant to temperature;

FIG. 4 schematically illustrates a configuration of areturn-light-attenuating module according to a first configurationexample;

FIG. 5 illustrates an axis-offset-fusion-splice of optical fibers usedin a first configuration example;

FIG. 6 schematically illustrates a configuration of areturn-light-attenuating module according to a second configurationexample;

FIG. 7 illustrates a high loss optical fiber used in the secondconfiguration example;

FIG. 8 schematically illustrates a configuration of areturn-light-attenuating module according to a third configurationexample;

FIG. 9 schematically illustrates a configuration of areturn-light-attenuating module according to a fourth configurationexample;

FIG. 10 is a cross-sectional view schematically illustrating aconfiguration of a return-light-attenuating module used in the fourthconfiguration example;

FIG. 11 schematically illustrates a configuration of areturn-light-attenuating module according to a fifth configurationexample;

FIG. 12 illustrates a schematic configuration of a terminal portionaccording to a configuration example 1;

FIG. 13 illustrates a schematic configuration of a terminal portionaccording to a configuration example 2;

FIG. 14 illustrates a schematic configuration of a terminal portionaccording to a configuration example 3;

FIG. 15 illustrates a schematic configuration of an optical fiber laserdevice according to a second embodiment of the present disclosure;

FIG. 16 illustrates a schematic configuration of an optical fiber laserdevice according to a third embodiment of the present disclosure;

FIG. 17 illustrates a schematic configuration of an optical fiber laserdevice according to a fourth embodiment of the present disclosure;

FIG. 18 illustrates a schematic configuration of an optical fiber laserdevice according to a fifth embodiment of the present disclosure;

FIG. 19 illustrates a schematic configuration of an optical fiber laserdevice according to a sixth embodiment of the present disclosure;

FIG. 20 illustrates a schematic configuration of an optical fiber laserdevice according to a seventh embodiment of the present disclosure;

FIG. 21 illustrates a schematic configuration of an optical fiber laserdevice according to an eighth embodiment of the present disclosure;

FIG. 22 illustrates a schematic configuration of an optical fiber laserdevice according to a ninth embodiment of the present disclosure;

FIG. 23 illustrates a schematic configuration of an optical fiber laserdevice according to a tenth embodiment of the present disclosure;

FIG. 24 illustrates a schematic configuration of an optical fiber laserdevice according to an eleventh embodiment of the present disclosure;

FIG. 25 illustrates a schematic configuration of an optical fiber laserdevice according to a twelfth embodiment of the present disclosure;

FIG. 26 illustrates a schematic configuration of an optical fiber laserdevice according to a thirteenth embodiment;

FIG. 27 illustrates a configuration of a return-light-attenuating moduleand its periphery;

FIG. 28 is a side plan view of the return-light-attenuating module;

FIG. 29 is a graph illustrating temperature of an optical fiber relativeto an input power to the return-light-attenuating module;

FIG. 30 is a graph illustrating an output power relative to the inputpower to the return-light-attenuating module;

FIG. 31 illustrates a schematic configuration of an optical fiber laserdevice according to a fourteenth embodiment;

FIG. 32 illustrates an example of resin-sealing a terminal of an opticalfiber at a terminal-treating portion;

FIG. 33 illustrates a schematic configuration of an optical fiber laserdevice according to a fifteenth embodiment;

FIG. 34 illustrates a schematic configuration of an optical fiber laserdevice according to a sixteenth embodiment;

FIG. 35 illustrates a schematic configuration of an optical fiber laserdevice according to a seventeenth embodiment;

FIG. 36 illustrates a schematic configuration of an optical fiber laserdevice according to an eighteenth embodiment;

FIG. 37 illustrates a schematic configuration of an optical fiber laserdevice according to a nineteenth embodiment;

FIG. 38 illustrates a schematic configuration of an optical fiber laserdevice according to a twentieth embodiment;

FIG. 39 illustrates a schematic configuration of an optical fiber laserdevice according to a twenty-first embodiment;

FIG. 40 illustrates a schematic configuration of an optical fiber laserdevice according to a twenty-second embodiment; and

FIG. 41 illustrates a schematic configuration of an optical fiber laserdevice according to a twenty-third embodiment.

DETAILED DESCRIPTION

Hereafter, embodiments of an optical fiber laser device according to thepresent disclosure will be explained in detail with reference to thedrawings. The present disclosure is not limited by the embodimentsexplained below. In all the drawings, identical or correspondingelements are given same reference numerals appropriately. It should benoted that the drawings show schematic examples. Accordingly, arelationship between respective elements may be different from realvalues. Among the drawings, there may be parts where the relationshipsand ratios of the illustrated sizes are different from one another. Inthe present description, cut-off wavelength means a cut-off wavelengthaccording to 22-m method defined by International TelecommunicationUnion Standardization Sector (ITU-T) G. 650.1. Any terms notspecifically defined in the description follow definitions and measuringmethods of the ITU-T G. 650.1.

First Embodiment

FIG. 1 illustrates a schematic configuration of an optical fiber laserdevice 100 according to a first embodiment. As illustrated in FIG. 1,the optical fiber laser device 100 according to the first embodiment isan optical fiber laser type device that generates laser light by usingan optical amplifying fiber 111 as an amplification medium in a laseroscillator 110.

The optical fiber laser device 100 includes an optical outputting fiber120, a return-light-attenuating portion (a return-light attenuationmodule 140), a thermal conversion unit 141, a temperature-monitoringdevice 150, and a control unit 160. The optical outputting fiber 120outputs output laser light L in a forward direction (arrow F in thedrawing) and to outside. The attenuation module 140 attenuates returnlight R propagating through at least the optical outputting fiber 120 ina reverse direction (arrow B in the drawing). The thermal conversionunit 141 is disposed in a return-light-attenuating module 140 andconvers the return light to heat. The temperature-monitoring device 150measures an increase in temperature, caused by heat generated in thethermal conversion unit 141, of the return-light-attenuating module 140.The control unit 160 decreases or stops an output of the output laserlight L when the temperature measured by the temperature-monitoringdevice 150 is equal to or more than a predetermined threshold. In theconfigurations of the embodiments explained below, the forward directionF and the reverse direction B are defined as illustrated in FIG. 1.

As illustrated in FIG. 1, the laser oscillator 110 includes the opticalamplifying fiber 111, a first light-reflecting unit 112 disposed on areverse direction side of the optical amplifying fiber 111 and a secondlight-reflecting unit 113 disposed on a forward direction side of theoptical amplifying fiber 111. At least the laser oscillator 110 andpreferably optical fibers, arranged in upstream and downstream of thelaser oscillator 110, from the optical outputting fiber 120 to a signalport optical fiber of a pumping-light multiplexer 114 are configured byan optical fiber including a core having characteristics that light ofwavelength of 1000 nm to 1200 nm is propagated in a substantially singlemode (single mode, or light having a mode field distribution most ofwhich is composed of a fundamental mode and the rest of which,approximately several percentages, is composed of several higher-ordermodes (a few modes)) in an electric field intensity distribution in acore of an optical fiber. Hereafter, a substantially single mode refersto a propagation mode of the light defined above. It is preferable thatthese optical fibers be configured to be approximately identical inmode-field diameter respectively at a wavelength of output laser light,and it is preferable that, for a core from the first light-reflectingunit 112 configuring at least the laser oscillator 110 to an opticalfiber configuring the second light-reflecting unit 113, a mode-fielddiameter at a wavelength of the output laser light be approximatelyidentical and mode propagation characteristics be configuredapproximately identical.

The optical amplifying fiber 111 is a double-cladding-type optical fiberwhose core portion made of a silica-based glass is doped with anytterbium (Yb) ion that is an amplification substance. An inner claddinglayer made of a silica-based glass and an outer cladding layer made of aresin or the like are formed in this order on an outer periphery of thecore portion of the optical amplifying fiber 111. The core portion whosenumerical aperture is for example 0.08 is configured to propagate lightof wavelength of 1000 nm to 1200 nm in single mode. The length of theoptical amplifying fiber 111 is, for example, 25 m. The absorptioncoefficient for the core portion of the optical amplifying fiber 111 is,for example, 200 dB/m at a wavelength of 1070 nm. A power conversionefficiency of pumping light input to the core portion to the oscillatedlaser light is, for example, 70%.

The first light-reflecting unit 112 and the second light-reflecting unit113 include, for example, fiber bragg gratings (FBGs) having differentwavelength characteristics. The first light-reflecting unit 112 and thesecond light-reflecting unit 113 are configured by providing adiffraction grating on the core of the optical fiber. It is preferablethat the first light-reflecting unit 112 and the second light-reflectingunit 113 be configured to be a double-cladding-type optical fiber havingan inner cladding, and the inner cladding be configured to propagatelight of a pumping-light wavelength in multi-mode.

The center wavelength of the first light-reflecting unit 112 is, forexample, 1070 nm, and the reflectivity of the first light-reflectingunit 112 is approximately 100% at the center wavelength andapproximately 2 nm of wavelength bandwidth including the centerwavelength. The first light-reflecting unit 112 has characteristics oftransmitting most of light at a wavelength of 915 nm therethrough. Onthe other hand, the center wavelength of the second light-reflectingunit 113 is, for example, 1070 nm which is approximately identical tothat of the first light-reflecting unit 112, the reflectivity of thesecond light-reflecting unit 113 is approximately 10% to 30% at thecenter wavelength, and the full width at half maximum in a reflectionwavelength bandwidth is approximately 1 nm. The second light-reflectingunit 113 has characteristics of transmitting most of the light at thewavelength of 915 nm therethrough. When pumping light of, for example, awavelength of 975 nm but not 915 nm is used, it is preferable for thefirst light-reflecting unit 112 and the second light-reflecting unit 113to have characteristics of transmitting most of the light of thewavelength of 975 nm therethrough.

By the above-described configuration, the laser oscillator 110configured to oscillate laser light of wavelength of 1070 nm whenpumping light of the wavelength of 915 nm is introduced and output thelaser light from the second light-reflecting unit 113 to the opticaloutputting fiber 120.

By the above-described configuration, the laser oscillator 110 isconfigured to oscillate laser light of wavelength of 1070 nm whenpumping light of the wavelength of 915 nm is introduced to the opticalamplifying fiber 111 and output the laser light from the secondlight-reflecting unit 113 to the optical outputting fiber 120.

When the optical fiber laser device 100 is used for laser-processing,the output laser light L output to the optical outputting fiber 120 isirradiated to a workpiece W via an irradiation head 121. The outputlaser light L irradiated to the workpiece W generates a reflected lighton a surface of the workpiece W, and a part of this reflected light maybe introduced to the optical outputting fiber 120 via the irradiationhead 121. The reflected light introduced to the optical outputting fiber120 may propagate through the core of the optical outputting fiber 120in the reverse direction and transmit through the first light-reflectingunit 112. Similarly, a Raman scattering light, a stimulated Brillouinscattering light, and the like generated from the reflected light maytransmit through the first light-reflecting unit 112 and reach aterminal portion 130. Therefore, a plurality of components are supposedto be included in the light transmitting through the firstlight-reflecting unit 112, and in the present description, lightpropagating through at least the core of the optical outputting fiber120 in the reverse direction of the output laser light L is calledreturn light R.

As illustrated in FIG. 1, the optical fiber laser device 100 accordingto the first embodiment adopts a so-called forward-pumping typeconfiguration. In the optical fiber laser device 100, the pumping-lightmultiplexer 114 for outputting pumping light to the firstlight-reflecting unit 112 is provided upstream to the firstlight-reflecting unit 112. Hereby the optical fiber laser device 100introduces the pumping light from the upstream to the firstlight-reflecting unit 112 toward the optical amplifying fiber 111.

The pumping-light multiplexer 114 includes, for example, a tapered fiberbundle (TFB). The pumping-light multiplexer 114 includes aforward-direction-side signal port optical fiber and areverse-direction-side signal port optical fiber, which configure twoend portions, and a plurality of pumping-light port optical fibers.Extending between the forward-direction-side signal port optical fiberand the reverse-direction-side signal port optical fiber is a core whichis preferable to have single mode propagation characteristics at a laseroscillation wavelength but may be a substantially single mode. on theother hand, the port for pumping light is configured by an optical fiberincluding a (multi-mode) core having multi-mode propagationcharacteristics at the pumping-light wavelength. A multi-mode core of amulti-mode optical fiber configuring each port for pumping light isconfigured to surround around the core of the optical fiber configuringthe forward-direction-side signal port.

The forward-direction-side signal port of the pumping-light multiplexer114 is connected to the double-cladding-type optical fiber so that thecore extending from the reverse-direction-side signal port is coupled toa single mode core and the core extending from each port for pumpinglight is coupled to an inner cladding. Moreover, thisdouble-cladding-type optical fiber is connected to the opticalamplifying fiber 111 via the first light-reflecting unit 112. Hereby thelight input to the reverse-direction-side signal port at the laseremission wavelength is propagated to the core of the optical amplifyingfiber 111 at a substantially single mode. On the other hand, the lightinput to each port for pumping light at the pumping wavelength ispropagated to the inner cladding of the optical amplifying fiber 111 inmulti-mode.

In the optical fiber laser device 100, the port for pumping light of thepumping-light multiplexer 114 is connected to pumping laser diodes 115 aand 115 b.

The reverse-direction-side signal port of the pumping-light multiplexer114 is connected to the terminal portion 130. Since the cores extend attwo ends of the forward-direction-side signal port and thereverse-direction-side signal port, the intensity of the return light isstrong, and thus, the reverse-direction-side signal port of thepumping-light multiplexer 114 is preferable for a port to be connectedto the terminal portion 130. However, the terminal portion 130 is notlimited to one that is connected to the reverse-direction-side signalport of the pumping-light multiplexer 114. For example, thepumping-light multiplexer 114 includes a plurality of pumping-lightports, and not all the port for pumping light are connected to thepumping laser diode. Therefore, a so-called dummy port may exist whichis not connected to a pumping laser diode. In such a case, the redundantport may be connected possibly to the terminal portion 130 of thepresent embodiment. When a plurality of redundant ports exist, it ispreferable to select one of the redundant ports which is the maximum inthe intensity of the return light and connect the selected one to theconfiguration of the terminal portion 130. There is an application inwhich other instruments are connected to the reverse-direction-sidesignal port of the pumping-light multiplexer 114 as well, and in such acase, the port for pumping light, which is the maximum in the intensityof the return light, among the redundant ports is preferable for a portto which the terminal portion 130 is connected. Although FIG. 1illustrates only one terminal portion 130, a plurality of terminalportions 130 may possibly exist in the optical fiber laser device 100,and in such a case, the present disclosure may be applied to at leastone of the plurality of the terminal portions 130. Certainly, thepresent disclosure may be simultaneously applied to the plurality of theterminal portions 130.

As illustrated in FIG. 1, the terminal portion 130 of the optical fiberlaser device 100 includes the return-light-attenuating module 140. Inthe example illustrated in FIG. 1, the terminal portion 130 includesonly the return-light-attenuating module 140; however, as will bedescribed hereafter in detail, the terminal portion 130 may includeother components.

As illustrated in FIG. 1, the return-light-attenuating module 140includes the thermal conversion unit 141 converting the return lightoutput from the pumping-light multiplexer 114 to heat, a thermalconductor 142 disposed to contact the thermal conversion unit 141 andconducting heat emitted by the thermal conversion unit 141, and a firsttemperature measurement point 151 provided on the thermal conductor 142.The first temperature measurement point 151 is a position wheretemperature sensors such as a thermistor, thermocouple, and the like aredisposed.

As will be explained hereafter with reference to a specific example, thethermal conversion unit 141 is means for converting an optical energy ofthe return light to a thermal energy. The thermal conductor 142includes, for example, a metal plate, and the thermal conversion unit141 is fixed on the thermal conductor 142 with a resin, etc. Therefore,a measured temperature at the first temperature measurement point 151provided on the thermal conductor 142 reflects the heat generated by thethermal conversion unit 141 appropriately. The heat generated by thethermal conversion unit 141 reflects a thermal load which the opticalfiber receives at the terminal portion 130. As a result, the measuredtemperature at the first temperature measurement point 151 provided onthe thermal conductor 142 is supposed to reflect the thermal load whichthe optical fiber receives at the terminal portion 130.

The temperature-monitoring device 150 converts an electric signal suchas a voltage, etc. obtained from a temperature sensor such as athermistor, thermocouple, and the like provided at the first temperaturemeasurement point 151 into information on temperature at the firsttemperature measurement point 151.

In the optical fiber laser device 100, it is preferable to disposetemperature sensors such as a thermistor, thermocouple, and the like ata second temperature measurement point 152 which may be regarded as areference point for measuring a temperature in the optical fiber laserdevice 100. The measured temperature at the first temperaturemeasurement point 151 provided on the thermal conductor 142 reflects thethermal load which the optical fiber at the terminal portion 130receives, however, the measured temperature may be affected sometimes bya thermal external disturbance other than the heat generated by theoptical fiber at the terminal portion 130. Therefore, a situation mayoccur that the thermal load which the optical fiber receives at theterminal portion 130 may not correctly be reflected to measuredtemperature at the first temperature measurement point 151 due to thethermal external disturbance other than the heat generated by theoptical fiber at the terminal portion 130.

To address this, temperature sensors such as a thermistor, thermocouple,and the like are disposed at the second temperature measurement point152 which may be regarded as a reference point for measuring atemperature in the optical fiber laser device 100 so that a temperaturedifference between a temperature at the first temperature measurementpoint 151 and a temperature at the second temperature measurement point152 is measured by the temperature-monitoring device 150. For example,the second temperature measurement point 152 may be a predeterminedpoint of a heatsink for cooling other heat-generating components such aspumping laser diodes 115 a and 115 b, the optical amplifying fiber 111,and the like. The thermal conductor 142 conducting the heat of thethermal conversion unit 141 may be contacted to the heatsink.

By the above-described configuration, it is possible to restrain anexternal disturbance by other heat-generating components such as thepumping laser diodes 115 a and 115 b, the optical amplifying fiber 111,and the like by subtracting the temperature at the second temperaturemeasurement point 152 from the temperature at the first temperaturemeasurement point 151, and thus measure the thermal load which theoptical fiber receives at the terminal portion 130 more accurately.

Information, obtained by the temperature-monitoring device 150, on thetemperature at the first temperature measurement point 151, or on thetemperature difference between the temperature at the first temperaturemeasurement point 151 and the temperature at the second temperaturemeasurement point 152 is transmitted to the control unit 160. Thetemperature-monitoring device 150 may be configured as one of thefunctions of the control unit 160. The control unit 160 may not be aspecial control unit for carrying out the present disclosure but may bea common general-purpose controller.

For example, the control unit 160 includes a central processing unit(CPU), a read only memory (ROM), a random access memory (RAM), aninterface (I/F), and a bus connecting them mutually. The CPU controlsrespective portions based on a program and data stored in the ROM. TheROM is a non-volatile semiconductor memory device and stores the programand the data. The RAM is a volatile semiconductor memory deviceoperating as a working area when carrying out the program by the CPU.The I/F is configured by, for example, a digital-analog converter (DAC)and an analog-digital converter (ADC), etc. The I/F converts digitaldata supplied by the CPU to an analogue signal and supplies theconverted analogue signal to each controlled site such as the pumpinglaser diodes 115 a and 115 b, and converts an analog electric currentsignal from the thermistor, thermocouple, and the like to a digitalsignal. The bus is a signal line group that connects CPU, ROM, RAM, andI/F mutually and enables data transaction among them. The control unit160 is not limited to a CPU or the like but may be a digital signalprocessor (DSP) or a device that utilizes an analogue control methodinstead of a digital control method.

The control unit 160 compares a temperature obtained by thetemperature-monitoring device 150 at the first temperature measurementpoint 151 with a predetermined threshold to supply a control signal fordecreasing, or stopping, an output to the pumping laser diodes 115 a and115 b when the temperature at the first temperature measurement point151 is equal to or more than the predetermined threshold. It ispreferable that the threshold be set at a value with a predeterminedmargin, for example, to an experimentally obtained temperature regardedto generate a thermal damage to an optical fiber such as a fiber fuse.As described in the above, it is preferable that the control unit 160compares the temperature difference between the temperature at the firsttemperature measurement point 151 and the temperature at the secondtemperature measurement point 152 with the predetermined threshold sincemore accurate measurement of thermal load which the optical fiberreceives at the terminal portion 130 is possible.

The pumping laser diodes 115 a and 115 b receiving the control signalfor decreasing or stopping the output decrease or stop the output of thepumping light introduced to the laser oscillator 110. Then, the outputlaser light L output by the optical fiber laser device 100 is decreasedor stopped, and the return light R introduced to the optical outputtingfiber 120 via the irradiation head 121 is also decreased or stopped. Asa result, a load which the optical fiber receives at the terminalportion 130 is restrained, and thus, the optical fiber laser device 100achieves high durability and high output capability.

FIGS. 2 and 3 are graphs illustrating examples of determinations,conducted by the control unit 160, using a threshold relating to atemperature. For comparison, FIGS. 2 and 3 also include graphsillustrating examples of determinations using a threshold related to theintensity of the return light. The determinations using a thresholdrelated to the intensity of the return light refers to a method ofdetermination in which, for example, the intensity of the return lightis detected by a light-receiving element, etc. and a threshold relativeto the intensity of the received light is used. In FIGS. 2 and 3, anupper graph (a) illustrates an example of determination using thethreshold related to the intensity of the return light and a lower graph(b) illustrates an example of determination using the threshold relatedto temperature. In the respective drawings, the upper graph (a) and thelower graph (b) are graphs sharing a time axis t (horizontal axis) andrelating to identical time-variation of the return light. In therespective drawings, a vertical axis I of the upper graph (a) indicatesthe intensity of the return light, and a vertical axis T of the lowergraph (b) indicates the measured temperature.

As illustrated in FIG. 2, the intensity of the return light variessteeply relative to time progression, and on the other hand, themeasured temperature varies relatively modestly relative to timeprogression. The intensity of the return light corresponds to anincreasing degree of the measured temperature and a temperature whenbeing saturated. Therefore, even if the intensity of the return lightreaches equal to or more than the value I₀ as seen between time t₀ andtime t₁, and even if the increasing degree of the measured temperatureis high, the measured temperature does not reach threshold T₀ if thetime length is short. In such a case, since the load which the opticalfiber receives at the terminal portion 130 is not so great that damageis generated on the optical fiber from a view point of time history, itis not necessary to restrain the output laser light L output by theoptical fiber laser device 100.

On the other hand, as seen between time t₂ and time t₃, when a timelength in which a state of the higher intensity of the return light islong, the measured temperature is supposed to reach equal to or morethan threshold T₀. In this case, the control unit 160 is supposed toconduct, at the time t₃, a controlling action for restraining the outputlaser light L output by the optical fiber laser device 100.

In another example illustrated in FIG. 3, the time length in which theintensity of the return light reaches equal to or more than the value I₀between time t₁₀ and time t₁₁, between time t₁₂ and time t₁₃, andbetween time t₁₄ and time t₁₅, and thus, a situation in which theintensity of the return light is high is repeated intermittently. Insuch a case, the measured temperature decreases sufficiently during thetime length in which the intensity of the return light is low such asbetween time t₁₁ and time t₁₂, between time t₁₃ and time t₁₄, and thelike. In such a case, since the load which the optical fiber receives atthe terminal portion 130 is not great, it is not necessary to restrainthe output laser light L output by the optical fiber laser device 100.

As understood from the above-described examples, the optical fiber laserdevice 100 determines the amount of load which the optical fiberreceives at the terminal portion 130 in consideration of not only theintensity of the return light but also a time period during which astate continues in which the return light is high power. Hereby, thedetermination as to whether the output laser L output by the opticalfiber laser device 100 is restrained is optimized, and thus, restrainingunnecessary output laser light L, that is, decrease in output orstoppage operation for unnecessary output laser L becomes fewer. As aresult, of the optical fiber laser device 100 achieves high durabilityand high output capability.

Hereafter, a configuration example of the return-light-attenuatingmodule 140 is explained. In the embodiment of the present disclosure,various configuration examples may be considered in the configuration ofthe return-light-attenuating module 140. Configuration examplesexplained below are illustrative of the return-light-attenuating module140, and each configuration example may replace thereturn-light-attenuating module 140 in the optical fiber laser device100. Therefore, only portions corresponding to thereturn-light-attenuating module 140 are described in the below-explainedconfiguration examples, and other portions may be regarded as identicalto those of the optical fiber laser device 100.

First Configuration Example of Return-Light-Attenuating Module

FIG. 4 schematically illustrates a configuration of areturn-light-attenuating module 140 a, and FIG. 5 illustrates anaxis-offset-fusion-splice portion 141 a of an optical fiber used in thefirst configuration example. As illustrated in FIG. 4, thereturn-light-attenuating module 140 a according to the firstconfiguration example includes an optical fiber 144 a which has beensubjected to an axis-offset-fusion-splice 141 a, and a thermal conductor142 a conducting a heat generated by the axis-offset-fusion-splice 141a.

The return-light-attenuating module 140 a according to the firstconfiguration example uses the axis-offset-fusion-splice portion 141 aof the optical fiber 144 a as a thermal conversion unit converting thereturn light R having been propagated to the optical fiber 144 a at theterminal portion to heat. In the return-light-attenuating module 140 a,the axis-offset-fusion-splice portion 141 a of the optical fiber 144 ais disposed at a thermal conductor 142 a, and the optical fiber 144 a isfixed on the thermal conductor 142 a with a fixing member such as, forexample, a silicone-based resin or the like. It is preferable to form agroove on a surface of the thermal conductor 142 a and to contain theoptical fiber 144 a in the groove.

A first temperature measurement point 151 a is set at a positionsuitable for measuring a heat generated by the axis-offset-fusion-spliceportion 141 a of the optical fiber 144 a via the thermal conductor 142a. That is, for example, it is preferable that the first temperaturemeasurement point 151 a be disposed in the vicinity of theaxis-offset-fusion-splice portion 141 a. The first temperaturemeasurement point 151 a is configured so that temperature sensors suchas a thermistor, thermocouple, and the like are disposed to be capableof measuring a temperature at the first temperature measurement point151 a.

A sealing portion 143 a provided at an end portion of the optical fiber144 a is a composing part for sealing an end of the optical fiber 144 a.

FIG. 5 is a cross-sectional view, of the optical fiber 144 a, in which aperiphery of the axis-offset-fusion-splice portion 141 a indicated as“X” in FIG. 4 is expanded. As illustrated in FIG. 5, the optical fiber144 a is fusion-spliced at the axis-offset-fusion-splice portion 141 aso that center axes of core 145 a are offset in a radial direction witheach other. Therefore, the return light R propagated through the opticalfiber 144 a is subjected to a huge loss at the axis-offset-fusion-spliceportion 141 a. That is, the return light R loses energy at theaxis-offset-fusion-splice portion 141 a, and the lost energy isconverted to a leakage light and heat. The heat is conducted to thethermal conductor 142 a via the fixing member, and the leakage lightreaches the thermal conductor 142 a via the fixing member and isconverted to heat there. A loss amount at the axis-offset-fusion-spliceportion 141 a may be adjusted with the number of position where theaxis-offset-fusion-splice portion 141 a is provided and an axis-offsetamount. Although, a coating 147 a is provided around a cladding 146 a ata portion separated from the axis-offset-fusion-splice portion 141 a inthe optical fiber 144 a illustrated in FIG. 5, the coating 147 a may beomitted. It is possible to make the coating 147 a be removed, inconsideration of affection by heat, at a periphery of theaxis-offset-fusion-splice portion 141 a or the entire of the opticalfiber 144 a.

The return-light-attenuating module 140 a configured as described aboveis a configuration example which may replace thereturn-light-attenuating module 140 in the optical fiber laser device100.

Second Configuration Example of Return-Light-Attenuating Module

FIG. 6 schematically illustrates a configuration areturn-light-attenuating module 140 b according to a secondconfiguration example, and FIG. 7 illustrates a high-loss optical fiber141 b used in the second configuration example. As illustrated in FIG.6, the return-light-attenuating module 140 b according to the secondconfiguration example includes an optical fiber 144 b provided with thehigh-loss optical fiber 141 b and a thermal conductor 142 b conducting aheat generated by the high-loss optical fiber 141 b.

The return-light-attenuating module 140 b according to the secondconfiguration example uses the high-loss optical fiber 141 b as athermal conversion unit converting the return light R having beenpropagated to the optical fiber 144 b at the terminal portion to heat.In the return-light-attenuating module 140 b, the high-loss opticalfiber 141 b to which the optical fiber 144 b is fusion-spliced isdisposed at the thermal conductor 142 b, and the optical fiber 144 b andthe high-loss optical fiber 141 b are fixed on the thermal conductor 142b with, for example, a silicone-based resin or the like.

A first temperature measurement point 151 b is set at a positionappropriate for measuring a heat generated by the high-loss opticalfiber 141 b via the thermal conductor 142 b. That is, for example, it ispreferable to dispose the first temperature measurement point 151 b inthe vicinity of a portion of the high-loss optical fiber 141 b. Thefirst temperature measurement point 151 b is configured so thattemperature sensors such as a thermistor, thermocouple, and the like aredisposed to be capable of measuring a temperature at the firsttemperature measurement point 151 b.

A sealing portion 143 b provided at an end portion of the high-lossoptical fiber 141 b is a composing part for sealing an end of thehigh-loss optical fiber 141 b.

FIG. 7 is a cross-sectional view of a fusion-spliced portion, expandedin FIG. 6 and indicated as “X”, of the optical fiber 144 b and thehigh-loss optical fiber 141 b. As illustrated in FIG. 7, a core 145 b ofthe high-loss optical fiber 141 b is formed of a material that isdifferent from that of the core of the optical fiber 144 b. For example,the core 145 b of the high-loss optical fiber 141 b is doped with ametallic impurity such as cobalt or the like. A cladding 146 b of thehigh-loss optical fiber 141 b may be identical to that of a cladding ofthe optical fiber 144 b.

By configuring in this manner, the return light R propagated through thehigh-loss optical fiber 141 b is subjected to a huge loss. That is, thereturn light R loses energy at the high-loss optical fiber 141 b, andthe lost energy is converted to a heat mainly. A loss amount at thehigh-loss optical fiber 141 b may be adjusted with a length of thehigh-loss optical fiber 141 b and the concentration of the metallicimpurity. Although a coating 147 b is provided around the cladding 146 bin the high-loss optical fiber 141 b illustrated in FIG. 7, the coating147 b is not always necessary. It is possible to make the coating 147 bbe in a removed state, in consideration of affection by heat, at aperiphery or the entire of the high-loss optical fiber 141 b.

The return-light-attenuating module 140 b configured as described aboveis a configuration example which may replace thereturn-light-attenuating module 140 in the optical fiber laser device100. The return-light-attenuating module 140 b described above may beconfigured such that the axis-offset-fusion-splice portion 141 a of thefirst configuration example is provided to the high-loss optical fiber141 b.

Third Configuration Example of Return-Light-Attenuating Module

FIG. 8 schematically illustrates a configuration of areturn-light-attenuating module 140 c according to a third configurationexample. As illustrated in FIG. 8, the return-light-attenuating module140 c according to the third configuration example includes an opticalfiber 144 c to which a bending portion 141 c is intentionally provided,and a thermal conductor 142 c conducting a heat generated by the bendingportion 141 c of the optical fiber 144 c.

The return-light-attenuating module 140 c according to the thirdconfiguration example uses a bending loss of the optical fiber 144 c asa thermal conversion unit converting the return light R propagated tothe optical fiber 144 c, which is a terminal portion, into heat. Thebending loss is a phenomenon in which a loss of the return light Rpropagating through the coiled optical fiber 144 c is higher than a lossof the return light R propagating through an optical fiber 144 c kept ina straight manner. Therefore, the return light R propagating through theoptical fiber 144 c intentionally provided with the bending portion 141c is supposed to be subjected to a huge loss. The loss amount may beadjusted with a bending radius and a length of the bending portion 141c.

In the return-light-attenuating module 140 c, the bending portion 141 cis disposed to the thermal conductor 142 c, and the optical fiber 144 cprovided with the bending portion 141 c is fixed on the thermalconductor 142 c with, for example, a silicone-based resin or the like.

A first temperature measurement point 151 c is set at a positionappropriate for measuring a heat generated by the bending portion 141 cof the optical fiber 144 c via the thermal conductor 142 c. That is, forexample, it is preferable to dispose the first temperature measurementpoint 151 c in the vicinity of the bending portion 141 c of the opticalfiber 144 c. The first temperature measurement point 151 c is configuredsuch that temperature sensors such as a thermistor, thermocouple, andthe like are disposed to be capable of measuring a temperature at thefirst temperature measurement point 151 c.

A sealing portion 143 c provided at an end portion of the optical fiber144 c is a composing part for sealing an end of the optical fiber 144 c.

The return-light-attenuating module 140 c configured as described aboveis a configuration example which may replace thereturn-light-attenuating module 140 in the optical fiber laser device100. The return-light-attenuating module 140 c described above may beconfigured to provide the bending portion 141 c to the high-loss opticalfiber 141 b of the second configuration example and provide theaxis-offset-fusion-splice portion 141 a of the first configurationexample to the bending portion 141 c.

Fourth Configuration Example of Return-Light-Attenuating Module

FIG. 9 schematically illustrates a configuration of areturn-light-attenuating module 140 d according to a fourthconfiguration example, and FIG. 10 is a cross-sectional viewschematically illustrating a configuration of an end of an optical fiber144 d used in the fourth configuration example. As illustrated in FIG.9, the return-light-attenuating module 140 d according to the fourthconfiguration example includes a sealing member 141 d sealing an end ofthe optical fiber 144 d and a thermal conductor 142 c conducting a heatgenerated by the sealing member 141 d.

The return-light-attenuating module 140 d according to the fourthconfiguration example uses the sealing member 141 d sealing the end ofthe optical fiber 144 d as a thermal conversion unit for converting thereturn light R propagating to the optical fiber 144 d, which is aterminal portion, into heat. The sealing member 141 d is, for example, aresin or the like and has characteristics of scattering or absorbing thereturn light R emitted from an endmost portion of the optical fiber 144d. The return light R scattered or absorbed by the sealing member 141 dgenerates heat at the sealing member 141 d directly or reaches a thermalconductor 142 d and generates heat indirectly.

In the return-light-attenuating module 140 d, the sealing member 141 dsealing the end of the optical fiber 144 d is provided to the thermalconductor 142 d, and the optical fiber 144 d is fixed on the thermalconductor 142 d with, for example, silicone-based resin or the like.

A first temperature measurement point 151 d is set at a positionappropriate for measuring heat generated by the sealing member 141 d viathe thermal conductor 142 d. That is, it is preferable that, forexample, the first temperature measurement point 151 d be disposed inthe vicinity of the sealing member 141 d. The first temperaturemeasurement point 151 d is configured so that temperature sensors suchas a thermistor, thermocouple, and the like are disposed to be capableof measuring a temperature at the first temperature measurement point151 d.

FIG. 10 is an expanded view of the end, sealed by the sealing member 141d, of the optical fiber 144 d. As illustrated in FIG. 10, a core 145 dand a cladding 146 d at the end of the optical fiber 144 d are cutobliquely relative to an optical axis of the optical fiber 144 d. It ishereby preferable since an amount of light, among the return lights R,reflected at the end of the optical fiber 144 d and returning to thecore decreases. When an intensity of the return light R is low, the core145 d and the cladding 146 d at the end of the optical fiber 144 d maybe in a state of being cut vertically relative to the optical axis ofthe optical fiber 144 d.

Although a coating 147 d is provided around the cladding 146 d in theoptical fiber 144 d illustrated in FIG. 10, the coating 147 d is notalways necessary. It is possible to remove the coating 147 d of theoptical fiber 144 d at the end portion or the entire coating 147 d inconsideration of affection by heat.

The return-light-attenuating module 140 d configured as described aboveis a configuration example which may replace thereturn-light-attenuating module 140 in the optical fiber laser device100. The configuration of sealing the end of the optical fiber 144 d ofthe return-light-attenuating module 140 d with the sealing member 141 dmay be applied to the sealing portions 143 a, 143 b, and 143 c in theabove-described first to third configuration examples.

Fifth Configuration Example of Return-Light-Attenuating Module

FIG. 11 schematically illustrates a configuration of areturn-light-attenuating module 140 e according to a fifth configurationexample. As illustrated in FIG. 11, the return-light-attenuating module140 e according to the fifth configuration example includes an opticalfiber 144 e and an irradiation surface 141 e, of a thermal conductor 142e, to which the return light R emitted from the end of the optical fiber144 e is irradiated.

The return-light-attenuating module 140 e according to the fifthconfiguration example uses the irradiation surface 141 e on the thermalconductor 142 e as a thermal conversion unit converting the return lightR propagating to the optical fiber 144 e, which is a terminal portion,into a heat. The irradiation surface 141 e on the thermal conductor 142e is a surface-treated metal surface to absorb the emitted ray andgenerate heat, and has a function of converting the return light Rpropagating to the optical fiber 144 e to a heat. That is, the heatemitted by the irradiation surface 141 e is one reflecting an intensityof the return light R including a time-history-based influence as well.

A first temperature measurement point 151 e is set at a positionappropriate for measuring a heat emitted by the irradiation surface 141e via a thermal conductor 142 e. That is, it is preferable that forexample, the first temperature measurement point 151 e be disposed inthe vicinity of the irradiation surface 141 e. The first temperaturemeasurement point 151 e is configured so that temperature sensors suchas a thermistor, thermocouple, and the like are disposed to be capableof measuring a temperature at the first temperature measurement point151 e.

As illustrated in FIG. 11, a core 145 e and a cladding 146 e at an endof the optical fiber 144 e are cut obliquely relative to an optical axisof the optical fiber 144 e. It is hereby preferable since an amount ofthe return light R reflected at the end of the optical fiber 144 edecreases. When an intensity of the return light R is low, the core 145e and the cladding 146 e at the end of the optical fiber 144 e may becut vertically relative to the optical axis of the optical fiber 144 e.

Although a coating 147 e is provided around the cladding 146 e in theoptical fiber 144 e illustrated in FIG. 11, the coating 147 e may not benecessary. It is possible to remove the coating 147 e at a periphery orthe entire of the optical fiber 144 e in consideration of affection byheat.

The return-light-attenuating module 140 e configured as described aboveis a configuration example which may replace thereturn-light-attenuating module 140 in the optical fiber laser device100.

Configuration Example of Terminal Portion

As described above, the terminal portion 130 of the optical fiber laserdevice 100 illustrated in FIG. 1 provided with only thereturn-light-attenuating module 140 may be configured to include othercomponents. Herein, a configuration example of the terminal portion 130including configurations other than the return-light-attenuating module140 will be explained. Configuration examples explained below areillustrative of the terminal portion 130, and each configuration examplemay replace the terminal portion 130 in the optical fiber laser device100. Therefore, only portions corresponding to the terminal portion 130are described in the configuration examples explained below, and otherconfigurations may be regarded as being identical to those of theoptical fiber laser device 100.

The configuration example for the terminal portion described hereafterincludes the return-light-attenuating module 140 as well. As describedabove, this return-light-attenuating module 140 may be replaced with thereturn-light-attenuating modules 140 a, 140 b, 140 c, 140 d, and 140 eaccording to the first to fifth configuration examples. Althoughexplanation of the configuration of the return-light-attenuating module140 omitted below may be regarded as configurations of those of thereturn-light-attenuating modules 140 a, 140 b, 140 c, 140 d, and 140 eaccording to the above-described first to fifth configuration examples.

Configuration Example 1 of Terminal Portion

FIG. 12 illustrates a schematic configuration of a terminal portion 131according to a configuration example 1. As illustrated in FIG. 12, theterminal portion 131 according to the configuration example 1 isconfigured to include a wavelength division multiplex opticalmultiplexer/demultiplexer 132, a visible-light-emitting portion 133, andthe return-light-attenuating module 140.

The visible-light-emitting portion 133 is a laser diode emitting, forexample, a red-colored laser light. As described above, the laser lightoutput by the optical fiber laser device 100 is of a wavelength of 1070nm and not a visible light range of laser light. Therefore, it isdifficult to confirm a position to which the output laser light isemitted. The visible-light-emitting portion 133 is a light source foroutputting a guide light G for confirming the position at which theoutput laser light is irradiated.

The wavelength division multiplex optical multiplexer/demultiplexer 132is an instrument for conducting wavelength-selective opticalmultiplexing/demultiplexing among an optical fiber through which thereturn light R is propagated, an optical fiber connected to thevisible-light-emitting portion 133, and an optical fiber connected tothe return-light-attenuating module 140. The wavelength divisionmultiplex optical multiplexer/demultiplexer 132 has wavelengthcharacteristics of transmitting the guide light G output by thevisible-light-emitting portion 133 with low loss to the optical fiberthrough which the return light R is propagated. On the other hand, thewavelength division multiplex optical multiplexer/demultiplexer 132 haswavelength characteristics of transmitting the return light R with lowloss to the optical fiber connected to the return-light-attenuatingmodule 140. The wavelength division multiplex opticalmultiplexer/demultiplexer 132 has wavelength characteristics ofattenuating the return light R to a large degree when transmitting thereturn light R to the optical fiber connected to thevisible-light-emitting portion 133.

By the above-described configuration, the terminal portion 131 accordingto the configuration example 1 includes: the return-light-attenuatingmodule 140 that attenuates the return light R propagating in at leastthe optical outputting fiber 120 in a reverse direction relative to theoutput laser light; and a visible-light-emitting portion 133 thatoutputs the guide light G for confirming the position to which theoutput laser light is irradiated.

Configuration Example 2 of Terminal Portion

FIG. 13 illustrates a schematic configuration of a terminal portion 134according to a configuration example 2. As illustrated in FIG. 13, theterminal portion 134 according to the configuration example 2 isconfigured to include an optical multiplexer/demultiplexer 135, anoptical sensor 136, and the return-light-attenuating module 140.

The optical multiplexer/demultiplexer 135 is an instrument known as aTap coupler and is an instrument conducting, while adjusting an opticalpower ratio, optical multiplexing/demultiplexing among the optical fiberthrough which the return light R is propagated, the optical fiberconnected to the optical sensor 136, and the optical fiber connected tothe return-light-attenuating module 140. The opticalmultiplexer/demultiplexer 135 splits the input return light R in returnlight R1 output to the return-light-attenuating module 140 and returnlight R2 output to the optical sensor 136. In this state, a splittingratio of optical intensities between the return light R1 and the returnlight R2 is, for example, 1:100 to 1:100000. Because of the splittingratio of these optical intensities, the opticalmultiplexer/demultiplexer 135 is called a 20 dB-to-50 dB coupler aswell.

The optical sensor 136 is configured by, for example, a photodiode. Theoptical sensor 136 configured by the photodiode is capable of monitoringan optical intensity of the return light R2 input to the optical sensor136 by converting the optical intensity of the input light to anelectric signal with a photoelectric effect. The intensity of the returnlight R2 input to the optical sensor 136 as described above is one thatthe optical multiplexer/demultiplexer 135 splits the return light R at apredetermined splitting ratio. Therefore, the optical sensor 136 iscapable of monitoring the optical intensity of the return light Rpropagating in the optical outputting fiber in the reverse directionrelative to the output laser light.

A result of monitoring by the optical sensor 136 may be used incombination with monitoring of the measured temperature at thereturn-light-attenuating module 140. For example, a history oftemperature measured by the return-light-attenuating module 140 and ahistory of optical intensity, monitored by the optical sensor 136, ofthe return light R monitored may be used to monitor a machined state atthe outputting portion of the optical fiber laser device. The monitoringof the measured temperature at the return-light-attenuating module 140and the monitoring of the return light R at the optical sensor 136 maybe conducted respectively by an instrument externally connected to anoutput terminal derived to outside of the optical fiber laser device.When the optical intensity of the return light R which the opticalsensor 136 monitors is equal to or less than a predetermined value,monitoring of the measured temperature at the return-light-attenuatingmodule 140 and the monitoring of the return light R at the opticalsensor 136 may be used to control to decrease or stop the output of thepumping light. When a fiber fuse occurs actually, the fiber fuse isprevented from occurring by using a phenomenon that an optical intensityof the return light R decreases when the fiber fuse occurs by any chanceand by monitoring the measured temperature at thereturn-light-attenuating module 140, it is possible to stop a progressof the fiber fuse with an optical intensity of the return light Rmonitored by the optical sensor 136.

By the above-described configuration, the terminal portion 134 accordingto configuration example 2 includes: the return-light-attenuating module140 that performs attenuation process to the return light R propagatingin at least the optical outputting fiber 120 in a reverse directionrelative to the output laser light; and the optical sensor 136 thatmonitors an optical intensity of the return light R propagating in theoptical outputting fiber in a reverse direction relative to the outputlaser light.

Configuration Example 3 of Terminal Portion

FIG. 14 illustrates a schematic configuration of a terminal portion 137according to a configuration example 3. As illustrated in FIG. 4, theterminal portion 137 according to the configuration example 3 includes awavelength division multiplex optical multiplexer/demultiplexer 132 a, avisible-light-emitting portion 133 a, an opticalmultiplexer/demultiplexer 135 a, an optical sensor 136 a, and thereturn-light-attenuating module 140. That is, the terminal portion 137according to the configuration example 3 is a combination of theabove-described terminal portion 131 according to the configurationexample 3 and the configuration of the terminal portion 134 according tothe configuration example 2. Therefore, many duplicated explanations areomitted in the present configuration example, and the omitted part ofdescription may be regarded as similar to the configuration example 1and the configuration example 2.

The visible-light-emitting portion 133 a is a light source foroutputting the guide light G for confirming a position to which theoutput laser light is irradiated. The wavelength division multiplexoptical multiplexer/demultiplexer 132 a is an instrument for conductingwavelength-selective optical multiplexing/demultiplexing among anoptical fiber through which the return light R is propagated, an opticalfiber connected to the visible-light-emitting portion 133 a, and anoptical fiber connected to the optical multiplexer/demultiplexer 135 a.

The wavelength division multiplex optical multiplexer/demultiplexer 132a has wavelength characteristics of transmitting the guide light Goutput by the visible-light-emitting portion 133 a with low loss to theoptical fiber through which the return light R is propagated. On theother hand, the wavelength division multiplex opticalmultiplexer/demultiplexer 132 a has wavelength characteristics oftransmitting the return light R with low loss to the optical fiberconnected to the optical multiplexer/demultiplexer 135 a. The wavelengthdivision multiplex optical multiplexer/demultiplexer 132 a haswavelength characteristics of attenuating the return light R to a largedegree when transmitting the return light R to the optical fiberconnected to the visible-light-emitting portion 133 a.

The optical multiplexer/demultiplexer 135 a is an instrument known as aTap coupler and is an instrument conducting, while adjusting an opticalpower ratio, optical multiplexing/demultiplexing among the optical fiberthrough which the return light R is propagated, the optical fiberconnected to the optical sensor 136 a, and the optical fiber connectedto the return-light-attenuating module 140. The optical sensor 136 a iscapable of monitoring an optical intensity of the return light Rpropagating through the optical outputting fiber in a reverse directionrelative to the output laser light.

By the above-described configuration, the terminal portion 137 accordingto the configuration example 3 includes: the return-light-attenuatingmodule 140 that performs attenuation process to the return light Rpropagating in at least the optical outputting fiber 120 in a reversedirection relative to the output laser light; the visible-light-emittingportion 133 a that outputs the guide light G for confirming a positionto which the output laser light is irradiated; and the optical sensor136 a that monitors an optical intensity of the return light Rpropagating in the optical outputting fiber in a reverse direction ofthe output laser light.

Modified Examples of Embodiments

Hereafter, modified examples of the optical fiber laser devicesaccording to the embodiments of the present disclosure will beexplained. Modified examples explained below are illustrative of theoptical fiber laser devices to which the present disclosure may beapplied. The modified examples explained below include configurations,which are shared with the optical fiber laser device 100 of the firstembodiment, such as the terminal portion 130, thereturn-light-attenuating module 140, and the like. Reference symbolsbeing identical to those of the first embodiment are given to theseconfigurations shared with the optical fiber laser device 100, andexplanations thereof will be omitted.

Second Embodiment

FIG. 15 illustrates a schematic configuration of an optical fiber laserdevice 200 according to a second embodiment of the present disclosure.As illustrated in FIG. 15, the optical fiber laser device 200 accordingto the second embodiment of the present disclosure is an optical fiberlaser type device that generates laser light by using the opticalamplifying fiber 111 as an amplification medium in the laser oscillator110.

As illustrated in FIG. 15, the optical fiber laser device 200 accordingto the second embodiment adopts a so-called backward-pumpingconfiguration. That is, the optical fiber laser device 200 introducespumping light backwardly relative to the laser oscillator 110.Therefore, the optical fiber laser device 200 includes, at the secondlight-reflecting unit 113, pumping light multiplexer 214 formultiplexing pumping light output by pumping laser diodes 215 a and 215b and outputting the pumping light to the second light-reflecting unit113.

The pumping-light multiplexer 214 is configured by, for example, a TFBsimilarly to the first embodiment. In the optical fiber laser device200, a light-pumping port of the pumping-light multiplexer 214 isconnected to the pumping laser diodes 215 a and 215 b and areverse-direction-side signal port of the pumping-light multiplexer 214is connected to the second light-reflecting unit 113. Theforward-direction-side signal port of the pumping-light multiplexer 214is connected to the optical outputting fiber 120. In the optical fiberlaser device 200, the terminal portion 130 is connected to the firstlight-reflecting unit 112. When a redundant port exists in thelight-pumping ports of the pumping-light multiplexer 214, the terminalportion 130 may be connected to the redundant port.

The optical fiber laser device 200 of the second embodiment configuredas described above is capable of determining an amount of load which theoptical fiber receives at the terminal portion 130 in consideration ofnot only the intensity of the return light but also a time length duringwhich a high intensity state of the return light continues. The controlunit 160 is capable of controlling outputs of the pumping laser diodes215 a and 215 b based on the amount of load which the optical fiberreceives at the terminal portion 130. Hereby, a determination as towhether the output laser light output by the optical fiber laser device200 is restrained is optimized, and thus, unnecessary restrain of theoutput laser light decreases. As a result, the optical fiber laserdevice 200 achieves high durability and high output capability.

Third Embodiment

FIG. 16 illustrates a schematic configuration of an optical fiber laserdevice 300 according to a third embodiment of the present disclosure. Asillustrated in FIG. 16, the optical fiber laser device 300 according tothe third embodiment of the present disclosure is an optical fiber lasertype device that generates laser light by using the optical amplifyingfiber 111 as an amplification medium in the laser oscillator 110.

As illustrated in FIG. 16, the optical fiber laser device 300 accordingto the third embodiment adopts a so-called bidirectional pumping typeconfiguration. That is, in the optical fiber laser device 300, pumpinglights are introduced forwardly and backwardly respectively relative tothe laser oscillator 110. Therefore, the optical fiber laser device 300includes, at an upstream to the first light-reflecting unit 112, apumping-light multiplexer 314 a multiplexing pumping lights output bypumping laser diodes 315 c and 315 d and outputting the pumping lightsto the first light-reflecting unit 112, and at a downstream to thesecond light-reflecting unit 113, a pumping-light multiplexer 314 bmultiplexing pumping lights output by pumping laser diodes 315 a and 315b and outputting the pumping lights to the second light-reflecting unit113.

The pumping-light multiplexers 314 a and 314 b are configured by, forexample, TFB similarly to the first embodiment. In the optical fiberlaser device 300, a light-pumping port of the pumping-light multiplexer314 a is connected to the pumping laser diodes 315 a and 315 b, and theforward-direction-side signal port of the pumping-light multiplexer 314a is connected to the first light-reflecting unit 112. A light-pumpingport of the pumping-light multiplexer 314 b is connected to the pumpinglaser diodes 315 c and 315 d, and the reverse-direction-side signal portof the pumping-light multiplexer 314 b is connected to the secondlight-reflecting unit 113. The forward-direction-side signal port of thepumping-light multiplexer 314 b is connected to the optical outputtingfiber 120.

The reverse-direction-side signal port of the pumping-light multiplexer314 a is connected to the terminal portion 130. However, similarly tothe first embodiment, the terminal portion 130 is not limited to oneconnected to the reverse-direction-side signal port of the pumping-lightmultiplexer 314 a. It may be configured that the terminal portion 130 isconnected to a so-called redundant port of the pumping-lightmultiplexers 314 a and 314 b.

The optical fiber laser device 300 of the third embodiment as configuredabove is capable of determine the amount of load which the optical fiberreceives at the terminal portion 130 in consideration of not only theintensity of the return light but also a time period during which a highintensity state of the return light continues. The control unit 160 iscapable of controlling outputs of the pumping laser diodes 315 a, 315 b,315 c, and 315 d based on the amount of load which the optical fiberreceives at the terminal portion 130. Hereby, a determination as towhether the output laser light output by the optical fiber laser device300 is restrained is optimized, and thus, unnecessary restrain of theoutput laser light decreases. As a result, the optical fiber laserdevice 300 achieves high durability and high output capability.

Fourth Embodiment

FIG. 17 illustrates a schematic configuration of an optical fiber laserdevice 400 according to a fourth embodiment of the present disclosure.As illustrated in FIG. 17, the optical fiber laser device 400 accordingto the fourth embodiment of the present disclosure is an optical fiberlaser type device that generates laser light by using the opticalamplifying fiber 111 as an amplification medium in the laser oscillator110.

As illustrated in FIG. 17, the optical fiber laser device 400 accordingto the fourth embodiment adopts a so-called forward-pumping typeconfiguration. However, unlike the first embodiment, the optical fiberlaser device 400 introduces pumping light from a downstream of the firstlight-reflecting unit 112 toward the optical amplifying fiber 111forwardly. Provided between the first light-reflecting unit 112 and theoptical amplifying fiber 111 is a pumping-light multiplexer 414 formultiplexing pumping lights output by pumping laser diodes 415 a and 415b and outputting the pumping lights in a direction of the opticalamplifying fiber 111.

The pumping-light multiplexer 414 is configured by, for example, TFBsimilarly to the first embodiment. In the optical fiber laser device400, a light-pumping port of the pumping-light multiplexer 414 isconnected to the pumping laser diodes 415 a and 415 b, and aforward-direction-side signal port of the pumping-light multiplexer 414is connected to the optical amplifying fiber 111. Areverse-direction-side signal port of the pumping-light multiplexer 414is connected to the first light-reflecting unit 112. In the opticalfiber laser device 400, the terminal portion 130 is connected to thefirst light-reflecting unit 112. When a redundant port exists in thelight-pumping ports of the pumping-light multiplexer 414, the terminalportion 130 may be connected to the redundant port.

The optical fiber laser device 400 of the fourth embodiment configuredas described above is capable of determining an amount of load which theoptical fiber receives at the terminal portion 130 in consideration ofnot only the intensity of the return light but also a time length duringwhich a high intensity state of the return light continues. The controlunit 160 is capable of controlling outputs of the pumping laser diodes415 a and 415 b based on the amount of load which the optical fiberreceives at the terminal portion 130. Hereby, a determination as towhether the output laser light output by the optical fiber laser device400 is restrained is optimized, and thus, unnecessary restrain of theoutput laser light decreases. As a result, the optical fiber laserdevice 400 achieves high durability and high output capability.

Fifth Embodiment

FIG. 18 illustrates a schematic configuration of an optical fiber laserdevice 500 according to a fifth embodiment of the present disclosure. Asillustrated in FIG. 18, the optical fiber laser device 500 according tothe fifth embodiment of the present disclosure is an optical fiber lasertype device that generates laser light by using the optical amplifyingfiber 111 as an amplification medium in the laser oscillator 110.

As illustrated in FIG. 18, the optical fiber laser device 500 accordingto the fifth embodiment adopts a so-called backward-pumpingconfiguration. However, unlike the second embodiment, the optical fiberlaser device 500 introduces pumping light from an upstream of the secondlight-reflecting unit 113 toward the optical amplifying fiber 111backwardly. Provided between the second light-reflecting unit 113 andthe optical amplifying fiber 111 is a pumping-light multiplexer 514 formultiplexing pumping lights output by pumping laser diodes 515 a and 515b and outputting the pumping lights in a direction of the opticalamplifying fiber 111.

The pumping-light multiplexer 514 is configured by, for example, TFBsimilarly to the first embodiment. In the optical fiber laser device500, a light-pumping port of the pumping-light multiplexer 514 isconnected to the pumping laser diodes 515 a and 515 b, and areverse-direction-side signal port of the pumping-light multiplexer 514is connected to the optical amplifying fiber 111. Aforward-direction-side signal port of the pumping-light multiplexer 514is connected to the optical outputting fiber 120 via the secondlight-reflecting unit 113. In the optical fiber laser device 500, theterminal portion 130 is connected to the first light-reflecting unit112. When a redundant port exists in the light-pumping ports of thepumping-light multiplexer 514, the terminal portion 130 may be connectedto the redundant port.

The optical fiber laser device 500 of the fifth embodiment configured asdescribed above is capable of determining an amount of load which theoptical fiber receives at the terminal portion 130 in consideration ofnot only the intensity of the return light but also a time length duringwhich a high intensity state of the return light continues. The controlunit 160 is capable of controlling outputs of the pumping laser diodes515 a and 515 b based on the amount of load which the optical fiberreceives at the terminal portion 130. Hereby, a determination as towhether the output laser light output by the optical fiber laser device500 is restrained is optimized, and thus, unnecessary restrain of theoutput laser light decreases. As a result, the optical fiber laserdevice 500 achieves high durability and high output capability.

Sixth Embodiment

FIG. 19 illustrates a schematic configuration of an optical fiber laserdevice 600 according to a sixth embodiment of the present disclosure. Asillustrated in FIG. 19, the optical fiber laser device 600 according tothe sixth embodiment of the present disclosure is an optical fiber lasertype device that generates laser light by using the optical amplifyingfiber 111 as an amplification medium in the laser oscillator 110.

As illustrated in FIG. 18, the optical fiber laser device 600 accordingto the sixth embodiment adopts a so-called bidirectional pumping typeconfiguration. However, unlike the third embodiment, the optical fiberlaser device 600 introduces pumping light from a downstream of the firstlight-reflecting unit 112 toward the optical amplifying fiber 111forwardly, and introduces pumping light from an upstream of the secondlight-reflecting unit 113 toward the optical amplifying fiber 111backwardly. Provided between the first light-reflecting unit 112 and theoptical amplifying fiber 111 is a pumping-light multiplexer 614 a formultiplexing pumping lights output by pumping laser diodes 615 a and 615b and outputting the pumping lights in a direction of the opticalamplifying fiber 111. Provided between the second light-reflecting unit113 and the optical amplifying fiber 111 is a pumping-light multiplexer614 b for multiplexing pumping lights output by pumping laser diodes 615c and 615 d and outputting the pumping lights in a direction of theoptical amplifying fiber 111.

The pumping-light multiplexers 614 a and 614 b are configured by, forexample, TFB similarly to the first embodiment. In the optical fiberlaser device 600, a light-pumping port of the pumping-light multiplexer614 a is connected to the pumping laser diodes 615 a and 615 b, and aforward-direction-side signal port of the pumping-light multiplexer 614a is connected to the optical amplifying fiber 111. Areverse-direction-side signal port of the pumping-light multiplexer 614a is connected to the first light-reflecting unit 112. In the opticalfiber laser device 600, a light-pumping port of the pumping-lightmultiplexer 614 b is connected to the pumping laser diodes 615 c and 615d, and a reverse-direction-side signal port of the pumping-lightmultiplexer 614 b is connected to the optical amplifying fiber 111. Aforward-direction-side signal port of the pumping-light multiplexer 614b is connected to the optical outputting fiber 120. In the optical fiberlaser device 600, the terminal portion 130 is connected to the firstlight-reflecting unit 112. When a redundant port exists in thelight-pumping ports of the pumping-light multiplexer 614 a and 614 b,the terminal portion 130 may be connected to the redundant port.

The optical fiber laser device 600 of the sixth embodiment configured asdescribed above is capable of determining an amount of load which theoptical fiber receives at the terminal portion 130 in consideration ofnot only the intensity of the return light but also a time length duringwhich a high intensity state of the return light continues. The controlunit 160 is capable of controlling outputs of the pumping laser diodes615 a, 615 b, 615 c, and 615 d based on the amount of load which theoptical fiber receives at the terminal portion 130. Hereby, adetermination as to whether the output laser light output by the opticalfiber laser device 600 is restrained is optimized, and thus, unnecessaryrestrain of the output laser light decreases. As a result, the opticalfiber laser device 600 achieves high durability and high outputcapability.

Seventh Embodiment

FIG. 20 illustrates a schematic configuration of an optical fiber laserdevice 700 according to a seventh embodiment of the present disclosure.As illustrated in FIG. 20, the optical fiber laser device 700 accordingto the seventh embodiment of the present disclosure has a masteroscillator power-amplifier (MOPA) structure that generates laser lightby using the optical amplifying fiber 111 as an amplification medium inthe laser oscillator 110, and amplifies the laser light by using anoptical amplifying fiber 716 as an amplification medium in the opticalamplifier.

As illustrated in FIG. 20, the optical fiber laser device 700 accordingto the seventh embodiment of the present disclosure is configured inwhich new components are added to the configuration of the optical fiberlaser device 100 according to the first embodiment. Therefore, onlyadditional components will be explained here.

As illustrated in FIG. 20, the optical fiber laser device 700 accordingto the seventh embodiment of the present disclosure includes an opticalamplifying fiber 716, between the laser oscillator 110 and theirradiation head 121, functioning as an amplification medium for anoptical amplifier. Provided between the optical amplifying fiber 716 andthe second light-reflecting unit 113 is a pumping-light multiplexer 717for multiplexing pumping lights output by pumping laser diodes 718 a and718 b and outputting the pumping lights in a direction of the opticalamplifying fiber 716.

The pumping-light multiplexer 717 is configured by, for example, TFBsimilarly to the pumping-light multiplexer 114. In the optical fiberlaser device 700, a light-pumping port of the pumping-light multiplexer717 is connected to the pumping laser diodes 718 a and 718 b, and aforward-direction-side signal port of the pumping-light multiplexer 717is connected to the optical amplifying fiber 716. Areverse-direction-side signal port of the pumping-light multiplexer 717is connected to the second light-reflecting unit 113. When a redundantport exists in the light-pumping ports of the pumping-light multiplexer717, the terminal portion 130 may be connected to the redundant port.

Similarly to the optical amplifying fiber 111, the optical amplifyingfiber 716 is a double-cladding-type optical fiber in which a coreportion made of a silica-based glass is doped with a Yb ion that is anamplifying material, and in which an inner cladding layer made of asilica-based glass and an outer cladding layer made of a resin or thelike are formed in this order at an outer periphery of the core portion.

By the above-described configuration, the optical fiber laser device 700is capable of amplifying the laser light, oscillated by the laseroscillator 110, with the optical amplifying fiber 716 and outputting thelaser light to the optical outputting fiber 120.

In the optical fiber laser device 700 of the seventh embodimentconfigured as described above, the control unit 160 is capable ofdetermining an amount of load which the optical fiber receives at theterminal portion 130 in consideration of not only the intensity of thereturn light but also a time length during which a high intensity stateof the return light continues. The control unit 160 is capable ofcontrolling outputs of the pumping laser diodes 115 a and 115 b and/orthe pumping laser diodes 718 a and 718 b based on an amount of loadwhich the optical fiber receives at the terminal portion 130. Hereby, adetermination as to whether the output laser light output by the opticalfiber laser device 700 is restrained is optimized, and thus, unnecessaryrestrain of the output laser light decreases. As a result, the opticalfiber laser device 700 achieves high durability and high outputcapability.

Although the optical fiber laser device 700 of the above-describedseventh embodiment is configured in which the optical amplifying fiber716 and the pumping-light multiplexer 717 are added to the optical fiberlaser device 100 of the first embodiment, it is possible to configure toadd the optical amplifying fiber 716 and the pumping-light multiplexer717 to the optical fiber laser devices 200, 300, 400, 500, and 600 ofthe second to sixth embodiments.

Eighth Embodiment

FIG. 21 illustrates a schematic configuration of an optical fiber laserdevice 800 according to an eighth embodiment of the present disclosure.As illustrated in FIG. 21, the optical fiber laser device 800 accordingto the eighth embodiment of the present disclosure has the MOPAstructure generates laser light by using the optical amplifying fiber111 as an amplification medium in the laser oscillator 110, andamplifies the laser light by using an optical amplifying fiber 816 as anamplification medium in the optical amplifier.

As illustrated in FIG. 21, the optical fiber laser device 800 accordingto the eighth embodiment of the present disclosure is configured inwhich new components are added to the configuration of the optical fiberlaser device 100 according to the first embodiment. Therefore, onlyadditional components will be explained here.

As illustrated in FIG. 21, the optical fiber laser device 800 accordingto the eighth embodiment of the present disclosure includes an opticalamplifying fiber 816, between the laser oscillator 110 and theirradiation head 121, functioning as an amplification medium for anoptical amplifier. Provided between the optical amplifying fiber 816 andthe optical outputting fiber 120 is a pumping-light multiplexer 817 formultiplexing pumping lights output by pumping laser diodes 818 a and 818b, and outputting the pumping lights in a direction of the opticalamplifying fiber 816.

The pumping-light multiplexer 817 is configured by, for example, TFBsimilarly to the pumping-light multiplexer 114. In the optical fiberlaser device 800, a light-pumping port of the pumping-light multiplexer817 is connected to the pumping laser diodes 818 a and 818 b, and areverse-direction-side signal port of the pumping-light multiplexer 817is connected to the optical amplifying fiber 816. Aforward-direction-side signal port of the pumping-light multiplexer 817is connected to the optical outputting fiber 120. When a redundant portexists in the light-pumping ports of the pumping-light multiplexer 817,the terminal portion 130 may be connected to the redundant port.

Similarly to the optical amplifying fiber 111, the optical amplifyingfiber 816 is a double-cladding-type optical fiber in which a coreportion made of a silica-based glass is doped with a Yb ion that is anamplifying material, and in which an inner cladding layer made of asilica-based glass and an outer cladding layer made of a resin or thelike are formed in this order at an outer periphery of the core portion.

By the above-described configuration, the optical fiber laser device 800is capable of amplifying the laser light, oscillated by the laseroscillator 110, with the optical amplifying fiber 816 and outputting thelaser light to the optical outputting fiber 120.

In the optical fiber laser device 800 of the eighth embodimentconfigured as described above, the control unit 160 is capable ofdetermining an amount of load which the optical fiber receives at theterminal portion 130 in consideration of not only the intensity of thereturn light but also a time length during which a high intensity stateof the return light continues. The control unit 160 is capable ofcontrolling outputs of the pumping laser diodes 115 a and 115 b and/orthe pumping laser diodes 818 a and 818 b based on an amount of loadwhich the optical fiber receives at the terminal portion 130. Hereby, adetermination as to whether the output laser light output by the opticalfiber laser device 800 is restrained is optimized, and thus, unnecessaryrestrain of the output laser light decreases. As a result, the opticalfiber laser device 800 achieves high durability and high outputcapability.

Although the optical fiber laser device 800 of the above-describedeighth embodiment is configured in which the optical amplifying fiber816 and the pumping-light multiplexer 817 are added to the optical fiberlaser device 100 of the first embodiment, it is possible to configure toadd the optical amplifying fiber 816 and the pumping-light multiplexer817 to the optical fiber laser devices 200, 300, 400, 500, and 600 ofthe second to sixth embodiments.

Ninth Embodiment

FIG. 22 illustrates a schematic configuration of an optical fiber laserdevice 900 according to a ninth embodiment of the present disclosure. Asillustrated in FIG. 22, the optical fiber laser device 900 according tothe ninth embodiment of the present disclosure has the MOPA structurethat generates laser light by using the optical amplifying fiber 111 asan amplification medium in the laser oscillator 110, and that amplifiesthe laser light by using an optical amplifying fiber 916 as anamplification medium in the optical amplifier.

As illustrated in FIG. 22, the optical fiber laser device 900 accordingto the ninth embodiment of the present disclosure is configured in whichnew components are added to the configuration of the optical fiber laserdevice 100 according to the first embodiment. Therefore, only additionalcomponents will be explained here.

As illustrated in FIG. 22, the optical fiber laser device 900 accordingto the ninth embodiment of the present disclosure includes an opticalamplifying fiber 916, between the laser oscillator 110 and theirradiation head 121, functioning as an amplification medium for anoptical amplifier. Provided between the optical amplifying fiber 916 andthe second light-reflecting unit 113 is a pumping-light multiplexer 917a for multiplexing pumping lights output by pumping laser diodes 918 aand 918 b and outputting the pumping lights in a direction of theoptical amplifying fiber 916. Moreover, provided between the opticalamplifying fiber 916 and the optical outputting fiber 120 is apumping-light multiplexer 917 b for multiplexing pumping lights outputby pumping laser diodes 918 c and 918 d and outputting the pumpinglights in a direction of the optical amplifying fiber 916.

The pumping-light multiplexers 917 a and 917 b are configured by, forexample, TFBs similarly to the pumping-light multiplexer 114. In theoptical fiber laser device 900, a light-pumping port of thepumping-light multiplexer 917 a is connected to the pumping laser diodes918 a and 918 b, and a forward-direction-side signal port of thepumping-light multiplexer 917 a is connected to the optical amplifyingfiber 916. A reverse-direction-side signal port of the pumping-lightmultiplexer 917 a is connected to the second light-reflecting unit 113.Moreover, in the optical fiber laser device 900, a light-pumping port ofthe pumping-light multiplexer 917 b is connected to the pumping laserdiodes 918 c and 918 d, and a reverse-direction-side signal port of thepumping-light multiplexer 917 b is connected to the optical amplifyingfiber 916. A forward-direction-side signal port of the pumping-lightmultiplexer 917 b is connected to the optical outputting fiber 120. Whena redundant port exists in the light-pumping ports of the pumping-lightmultiplexers 917 a and 917 b, the terminal portion 130 may be connectedto the redundant port.

Similarly to the optical amplifying fiber 111, the optical amplifyingfiber 916 is a double-cladding-type optical fiber in which a coreportion made of a silica-based glass is doped with a Yb ion that is anamplifying material, and in which an inner cladding layer made of asilica-based glass and an outer cladding layer made of a resin or thelike are formed in this order at an outer periphery of the core portion.

By the above-described configuration, the optical fiber laser device 900is capable of amplifying the laser light, oscillated by the laseroscillator 110, with the optical amplifying fiber 916 and outputting thelaser light to the optical outputting fiber 120.

In the optical fiber laser device 900 of the ninth embodiment configuredas described above, the control unit 160 is capable of determining anamount of load which the optical fiber receives at the terminal portion130 in consideration of not only the intensity of the return light butalso a time length during which a high intensity state of the returnlight continues. The control unit 160 is capable of controlling outputsof the pumping laser diodes 115 a and 115 b and/or the pumping laserdiodes 918 a, 918 b, 918 c, and 918 d based on an amount of load whichthe optical fiber receives at the terminal portion 130. Hereby, adetermination as to whether the output laser light output by the opticalfiber laser device 900 is restrained is optimized, and thus, unnecessaryrestrain of the output laser light decreases. As a result, the opticalfiber laser device 900 achieves high durability and high outputcapability.

Although the optical fiber laser device 900 of the above-described ninthembodiment is configured in which the optical amplifying fiber 916 andthe pumping-light multiplexers 917 a and 917 b are added to the opticalfiber laser device 100 of the first embodiment, it is possible toconfigure to add the optical amplifying fiber 916 and the pumping-lightmultiplexers 917 a and 917 b to the optical fiber laser devices 200,300, 400, 500, and 600 of the second to sixth embodiments.

Tenth Embodiment

FIG. 23 illustrates a schematic configuration of an optical fiber laserdevice 1000 according to a tenth embodiment of the present disclosure.As illustrated in FIG. 23, the optical fiber laser device 1000 accordingto the tenth embodiment of the present disclosure has the MOPA structurethat generates laser light by using the optical amplifying fiber 111 asan amplification medium in the laser oscillator 110, and amplifies thelaser light by using the optical amplifying fiber 716 as anamplification medium in the optical amplifier.

As illustrated in FIG. 23, the optical fiber laser device 1000 accordingto the tenth embodiment of the present disclosure is configured in whichnew components are added to the configuration of the optical fiber laserdevice 700 according to the seventh embodiment. Therefore, onlyadditional components will be explained here.

As illustrated in FIG. 23, in the optical fiber laser device 1000, awavelength division multiplex optical multiplexer/demultiplexer 1031 isinserted between the optical amplifying fiber 716 and the irradiationhead 121, and an optical fiber between the optical amplifying fiber 716and the irradiation head 121 is split. The split optical fiber isconnected to a terminal portion 1030.

The terminal portion 1030 includes a wavelength division multiplexoptical multiplexer/demultiplexer 1032, a visible-light-emitting portion1033, and the return-light-attenuating module 140. That is, aconfiguration of the terminal portion 1030 is similar to the terminalportion 131 according to the configuration example 1 described above.Therefore, explanations for each configuration of the terminal portion1030 are omitted here, and each configuration of the terminal portion1030 of which explanations are omitted is regarded as being similar toeach configuration of the terminal portion 131 according to theconfiguration example 1.

The terminal portion 1030 includes the return-light-attenuating module140 that performs attenuation process to the return light R propagatingin the optical outputting fiber in a reverse direction of the outputlaser light; and the visible-light-emitting portion 1033 that outputsthe guide light for confirming a position to which the output laserlight is irradiated.

In the optical fiber laser device 1000 of the tenth embodiment, thecontrol unit 160 is capable of determining an amount of load which theoptical fiber receives at the terminal portion 1030 in consideration ofnot only the intensity of the return light but also a time length duringwhich a high intensity state of the return light continues. The controlunit 160 is capable of controlling outputs of the pumping laser diodes115 a and 115 b and/or the pumping laser diodes 718 a and 718 b based onan amount of load which the optical fiber receives at the terminalportion 1030. Hereby, a determination as to whether the output laserlight output by the optical fiber laser device 1000 is restrained isoptimized, and thus, unnecessary restrain of the output laser lightdecreases. As a result, the optical fiber laser device 1000 achieveshigh durability and high output capability.

Although the optical fiber laser device 1000 of the above-describedtenth embodiment is configured in which the terminal portion 1030 isadded to the optical fiber laser device 700 of the seventh embodiment,it is possible to configure to add the terminal portion 1030 to thelaser devices of the other embodiments similarly.

Eleventh Embodiment

FIG. 24 illustrates a schematic configuration of an optical fiber laserdevice 1100 according to an eleventh embodiment of the presentdisclosure. As illustrated in FIG. 24, the optical fiber laser device1100 according to an eleventh embodiment of the present disclosure hasthe MOPA structure that generates laser light by using the opticalamplifying fiber 111 as an amplification medium in the laser oscillator110, and amplifies the laser light by using the optical amplifying fiber716 as an amplification medium in the optical amplifier.

As illustrated in FIG. 24, the optical fiber laser device 1100 accordingto the eleventh embodiment of the present disclosure is configured inwhich new components are added to the configuration of the optical fiberlaser device 700 according to the seventh embodiment. Therefore, onlyadditional components will be explained here.

As illustrated in FIG. 24, in the optical fiber laser device 1100, anoptical multiplexer/demultiplexer 1131 is inserted between the opticalamplifying fiber 716 and the irradiation head 121, and an optical fiberbetween the optical amplifying fiber 716 and the irradiation head 121 issplit. The split optical fiber is connected to a terminal portion 1130.

The terminal portion 1130 includes an optical multiplexer/demultiplexer1132, an optical sensor 1133, and the return-light-attenuating module140. That is, a configuration of the terminal portion 1130 is similar tothe terminal portion 134 according to the configuration example 2described above. Therefore, explanations for each configuration of theterminal portion 1130 are omitted here, and each configuration of theterminal portion 1130 of which explanations are omitted is regarded asbeing similar to each configuration of the terminal portion 134according to the configuration example 2.

The terminal portion 1130 includes: the return-light-attenuating module140 that performs attenuation process to the return light R propagatingin the optical outputting fiber in a reverse direction of the outputlaser light; and the optical sensor 1133 that monitors an opticalintensity of the return light R propagating in the optical outputtingfiber in a reverse direction of the output laser light.

In the optical fiber laser device 1100 of the eleventh embodiment, thecontrol unit 160 is capable of determining an amount of load which theoptical fiber receives at the terminal portion 1130 in consideration ofnot only the intensity of the return light but also a time length duringwhich a high intensity state of the return light continues. The controlunit 160 is capable of controlling outputs of the pumping laser diodes115 a and 115 b and/or the pumping laser diodes 718 a and 718 b based onan amount of load which the optical fiber receives at the terminalportion 1130. Hereby, a determination as to whether the output laserlight output by the optical fiber laser device 1100 is restrained isoptimized, and thus, unnecessary restrain of the output laser lightdecreases. As a result, the optical fiber laser device 1100 achieveshigh durability and high output capability.

Although the optical fiber laser device 1100 of the above-describedeleventh embodiment is configured in which the terminal portion 1130 isadded to the optical fiber laser device 700 of the seventh embodiment,it is possible to configure to add the terminal portion 1130 to thelaser devices of the other embodiments similarly.

Twelfth Embodiment

FIG. 25 illustrates a schematic configuration of an optical fiber laserdevice 1200 according to a twelfth embodiment of the present disclosure.As illustrated in FIG. 25, the optical fiber laser device 1100 accordingto an eleventh embodiment of the present disclosure has the MOPAstructure that generates laser light by using the optical amplifyingfiber 111 as an amplification medium in the laser oscillator 110, andamplifies the laser light by using the optical amplifying fiber 716 asan amplification medium in the optical amplifier.

As illustrated in FIG. 25, the optical fiber laser device 1200 accordingto the twelfth embodiment of the present disclosure is configured inwhich new components are added to the configuration of the optical fiberlaser device 700 according to the seventh embodiment. Therefore, onlyadditional components will be explained here.

As illustrated in FIG. 25, in the optical fiber laser device 1200, anoptical multiplexer/demultiplexer 1231 is inserted between the opticalamplifying fiber 716 and the irradiation head 121, and an optical fiberbetween the optical amplifying fiber 716 and the irradiation head 121 issplit. The split optical fiber is connected to a terminal portion 1230.In the optical fiber laser device 1200 according to the twelfthembodiment, a wavelength division optical multiplexer/demultiplexer maybe used in place of the optical multiplexer/demultiplexer 1231.

The terminal portion 1230 includes a wavelength division multiplexoptical multiplexer/demultiplexer 1232, a visible-light-emitting portion1233, an optical multiplexer/demultiplexer 1234, an optical sensor 1235,and the return-light-attenuating module 140. That is, a configuration ofthe terminal portion 1230 is similarly to the terminal portion 137according to the configuration example 3 described above. Therefore,explanations for each configuration of the terminal portion 1230 isomitted here, and each configuration of the terminal portion 1230 ofwhich explanations are omitted is regarded as being similar to eachconfiguration of the terminal portion 137 according to the configurationexample 3.

The terminal portion 1230 includes: the return-light-attenuating module140 that performs attenuation process to the return light R propagatingin the optical outputting fiber in a reverse direction of the outputlaser light; the visible-light-emitting portion 1233 that outputs theguide light for confirming a position to which the output laser light isirradiated; and the optical sensor 1235 that monitors an opticalintensity of the return light R propagating in the optical outputtingfiber in a reverse direction of the output laser light.

In the optical fiber laser device 1200 of the twelfth embodiment, thecontrol unit 160 is capable of determining an amount of load which theoptical fiber receives at the terminal portion 1230 in consideration ofnot only the intensity of the return light but also a time length duringwhich a high intensity state of the return light continues. The controlunit 160 is capable of controlling outputs of the pumping laser diodes115 a and 115 b and/or the pumping laser diodes 718 a and 718 b based onan amount of load which the optical fiber receives at the terminalportion 1230. Hereby, a determination as to whether the output laserlight output by the optical fiber laser device 1200 is restrained isoptimized, and thus, unnecessary restrain of the output laser lightdecreases. As a result, the optical fiber laser device 1200 achieveshigh durability and high output capability.

Although the optical fiber laser device 1200 of the above-describedtwelfth embodiment is configured in which the terminal portion 1230 isadded to the optical fiber laser device 700 of the seventh embodiment,it is possible to configure to add the terminal portion 1230 to thelaser devices of the other embodiments similarly.

Thirteenth Embodiment

FIG. 26 illustrates a schematic configuration of an optical fiber laserdevice 1300 according to a thirteenth embodiment. As illustrated in FIG.26, the optical fiber laser device 1300 according to the thirteenthembodiment is an optical fiber laser type device that generates outputlaser light by using an optical amplifying fiber 111 as an amplificationmedium in the laser oscillator 110.

As illustrated in FIG. 26, the optical fiber laser device 1300 accordingto the thirteenth embodiment adopts a so-called forward-pumping typeconfiguration. The optical fiber laser device 1300 is provided with thepumping-light multiplexer 114, at an upstream to the firstlight-reflecting unit 112, multiplexing pumping lights output by thepumping laser diodes 115 a and 115 b and outputting the pumping lightsto the optical amplifying fiber 111. Hereby the pumping lights areintroduced from the upstream to the first light-reflecting unit 112toward the optical amplifying fiber 111.

The pumping-light multiplexer 114 is configured by, for example, atapered fiber bundle (TFB). The pumping-light multiplexer 114 includesthe forward-direction-side signal port optical fiber and thereverse-direction-side signal port optical fiber, which configure twoend portions, and a plurality of pumping-light port optical fibers. Inthe optical fiber laser device 1300, a light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b.

A reverse-direction-side signal port of the pumping-light multiplexer114 is connected to a return-light-attenuating module 170. Since thecores extend at two ends of the forward-direction-side signal port andthe reverse-direction-side signal port, the intensity of the returnlight is great, and thus, the reverse-direction-side signal port of thepumping-light multiplexer 114 is preferable for a port to be connectedto the return-light-attenuating module 170. As illustrated in FIG. 26, avisible-light-emitting portion 180 introducing a visible light via thereturn-light-attenuating module 170 in a forward direction is connectedto the return-light-attenuating module 170. The return-light-attenuatingmodule 170 emits an attenuated return light from an end portion on anopposite side to the optical outputting fiber 120, and thevisible-light-emitting portion 180 is connected to the end portion.

FIG. 27 illustrates a configuration of the return-light-attenuatingmodule 170 and therearound. As illustrated in FIG. 27, thereturn-light-attenuating module 170 includes, as a primaryconfiguration, an optical fiber connecting from a reverse-direction-sidesignal port of the pumping-light multiplexer 114 to thevisible-light-emitting portion 180. The return-light-attenuating module170 includes a metal plate 173 fixing an optical receiving fiber 171 andan optical attenuating fiber 172 provided to thereturn-light-attenuating module 170 and configuring a thermal conversionportion for dissipating a heat generated when a leakage light from theoptical receiving fiber 171 and the optical attenuating fiber 172 isconverted to the heat. That is, the metal plate 173 is formed of a metalhaving high thermal conductivity, and the metal plate 173 itself isconnected to a heatsink or the like in the optical fiber laser device1300 and configured to dissipate the heat generated from the opticalreceiving fiber 171 and the optical attenuating fiber 172 effectively.

As illustrated in FIG. 27, the optical receiving fiber 171 and theoptical attenuating fiber 172 are connected respectively to a signalport optical fiber 114 a extending from a reverse-direction-side signalport of the pumping-light multiplexer 114 and a pigtail optical fiber181 extending from the visible-light-emitting portion 180. The signalport optical fiber 114 a and the optical receiving fiber 171 arefusion-spliced at a first fusion-spliced point 174 a, the opticalreceiving fiber 171 and the optical attenuating fiber 172 arefusion-spliced at a second fusion-spliced point 174 b, and the opticalattenuating fiber 172 and the pigtail optical fiber 181 arefusion-spliced at a third fusion-spliced point 174 c. A core of theoptical attenuating fiber 172 is connected, via the optical receivingfiber 171 and the signal port optical fiber 114 a and the like, to acore of an optical fiber such as the optical amplifying fiber 111 or thelike configuring the laser oscillator 110.

It is preferable to configure the first fusion-spliced point 174 a sothat a connection loss is fewer, for example, an approximately samedegree to a connection loss of the second fusion-spliced point 174 b, orsmaller than the connection loss of the second fusion-spliced point 174b. It is preferable to prevent, from a heat management point of view, aheat from being generated at the first fusion-spliced point 174 a and toconcentrate a heat-generating factor on the metal plate 173. It ispreferable to make the signal port optical fiber 114 a and the opticalreceiving fiber 171 approximately identical in core diameter and NA. Itis preferable to make a cladding diameter of the optical receiving fiber171 equal to or more than a cladding diameter of the signal port opticalfiber 114 a.

It is preferable to use so-called low-index optical fibers for thesignal port optical fiber 114 a and the optical receiving fiber 171. Arefractive index of a coating of the low-index optical fiber is lowerthan a refractive index of a cladding, and thus it is possible torestrain a low leakage light at the first fusion-spliced point 174 a,the low-index optical fiber contributes to concentration of aheat-generating factor on the metal plate 173.

From the view point described above, it is preferable that the opticalreceiving fiber 171 be selected in accordance with the optical fiber tobe connected to the return-light-attenuating module 170, for example,the signal port optical fiber 114 a in the present embodiment. Forexample, the optical receiving fiber 171 may be an optical fiber that isthe same as the optical fiber connected to the return-light-attenuatingmodule 170. In that case, a configuration of not providing the firstfusion-spliced point 174 a is possible as well.

Herein an example of combination of optical fibers will be illustrated.For example, when the signal port optical fiber 114 a is a pedestaloptical fiber of which core diameter is 14 μm and of which claddingdiameter is 125 μm, the optical receiving fiber 171 is a double-claddingoptical fiber of which core diameter is 14 μm and of which claddingdiameter is 125 μm. A pedestal optical fiber is an optical fiberconstructed so that an area, of which refractive index is between thoseof the core and the cladding, is provided around the core. In this case,propagation characteristics of the cores of the pedestal optical fiberand the double-cladding optical fiber are substantially single modesimilarly to the optical fiber configuring the laser oscillator 110.

It is not always necessary to configure the second fusion-spliced point174 b so that its connection loss is less than that of the firstfusion-spliced point 174 a. It is because the second fusion-splicedpoint 174 b is disposed on the metal plate 173 to be capable ofdissipating a heat caused by a connection loss. However, when the heatgenerated at the second fusion-spliced point 174 b is great to somedegree, a coating of the optical fiber may be melted sometimes by thegenerated heat. Therefore, it is preferable that the coating of theoptical fiber in the vicinity of the second fusion-spliced point 174 bbe removed in advance. It is more preferable that the coating of theoptical attenuating fiber 172 in a predetermined length be removed fromthe second fusion-spliced point 174 b since the optical attenuatingfiber 172 generates more heat.

Since it is not necessary to configure the second fusion-spliced point174 b so that the connection loss decreases, the optical attenuatingfiber 172 may be chosen in wide variety. If the optical attenuatingfiber 172 is chosen freely so that a bending loss in the return light isgreater than a bending loss in the visible light and this opticalattenuating fiber 172 is coiled for a plurality of rounds to be fixed tothe metal plate 173, the optical attenuating fiber 172 may serve as thereturn light propagation loss portion made of a medium causing a loss tothe return light continuously in a direction of propagation of thereturn light. Since a problematic component of the return lightpropagates in a core mode, it is preferable that, in the core of theoptical attenuating fiber 172, a loss at a wavelength of the returnlight be greater than a loss at a visible light wavelength rangerelative to the return light propagating in the core mode.

The visible-light-emitting portion 180 outputs a visible laser light in,for example, red, green, or the like as a visible light, and the visiblelaser light is output from the optical fiber laser device 1300 via thereturn-light-attenuating module 170, the optical amplifying fiber 111,and the optical outputting fiber 120. A length and a bending diameter ofthe optical attenuating fiber 172 configuring thereturn-light-attenuating module 170 in this state is set so that avisible laser light output from the optical fiber laser device 1300 hasa visible degree of optical intensity, and so that return light made ofinfrared light input to the return-light-attenuating module 170 isattenuated and output to the visible-light-emitting portion 180 side.The visible degree of optical intensity herein is, for example,approximately JIS C6802 class 2 to 3. The restrain means, for example,attenuation of a return light power input to the visible-light-emittingportion 180 by equal to or greater than approximately 300 W, or by adegree not damaging the visible-light-emitting portion 180 even if it isapproximately equal to or more than the output.

A wavelength of visible light is approximately 400 nm to 800 nm, and awavelength of output laser light L for laser machining is infraredlight, and is equal to or greater than 1000 nm in many cases. Therefore,it is preferable to choose the optical attenuating fiber 172 whosebending loss in light of wavelength of equal to or more than 1000 nm isgreater than a bending loss in light of wavelength of equal to or lessthan 800 nm. For example, it is more preferable that, when a wavelengthof a visible light used for a guide light is 660 nm and a wavelength ofoutput laser light L for laser-machining use is 1070 nm, the opticalattenuating fiber 172 be chosen so that a bending loss in light ofwavelength of 1070 nm is greater than a bending loss in light ofwavelength of 660 nm. It is preferable that a difference between thebending loss in the return light and the bending loss in the visiblelight be equal to or greater than 50 dB so that the visible light outputfrom the optical fiber laser device 1300 is visible and the return lightto the visible-light-emitting portion 180 is restrained. For example, ifa difference between a bending loss in the return light and a bendingloss in the visible light is equal to or greater than 50 dB, a majorportion of the return light is attenuated and subjected to thermalconversion at the optical attenuating fiber 172. The return light ofwhich major portion is attenuated at the optical attenuating fiber 172in this manner is attenuated to equal to or less than 10 mW if it is,for example, 500 W, and only a remaining light with a micro intensity issupposed to be output from the optical attenuating fiber 172.

It is preferable that a bend edge wavelength of the optical attenuatingfiber 172 be shorter than a wavelength of the return light. The bendedge wavelength is a wavelength at which an optical fiber without beingcoiled makes a fundamental mode propagate therethrough but does not makethe fundamental mode propagate therethrough if the wavelength is longerthan the bend edge wavelength (the longest wavelength at which thefundamental mode may be propagated with a low loss). That is, whenattempting the return light of which wavelength is longer than the bendedge wavelength through the coiled optical attenuating fiber 172, thepower of the return light may be significantly reduced. On the otherhand, a wavelength of the visible light being used as a guide light ismade shorter than the bend edge wavelength of the optical attenuatingfiber 172, preferably by equal to or longer than 100 nm.

It is preferable that the core of the optical attenuating fiber 172 beconfigured to propagate light that is at least used as a guide lightamong the visible lights at a substantially single mode. It is because aloss in the guide light may be decreased. Therefore, it is preferablethat the bend edge wavelength of the optical attenuating fiber 172 belonger than 660 nm, and longer than 800 nm is more preferable.

It is preferable that the bending radius of the optical attenuatingfiber 172 be set so that an amount of the bending loss in light beingused as a guide light is within a range in which a visible light outputfrom the optical fiber laser device as described above is visible. Forexample, it is preferable that the bending radius of the opticalattenuating fiber 172 be configured to vary by one round within a rangeof radii from 150 mm to 30 mm. As illustrated in FIG. 27, it is morepreferable that an end point of the optical attenuating fiber 172 at alarger bending radius side be connected to the optical receiving fiber171. It is because, it is an arrangement that the bending loss increasesgradually from a side at which the return light is incident since alarger bending radius is subjected to a smaller bending loss, and thus,it is possible to disperse a heat caused by the bending loss. Althoughit is possible to select the length of a section of the coiled opticalattenuating fiber 172 in accordance with the amount of the return lightto be attenuated, and it may be, for example, 1 m to 5 m.

An end at a smaller bending radius side of the optical attenuating fiber172 (an end on an opposite side to the optical outputting fiber 120) isfusion-spliced to the pigtail optical fiber 181 at a thirdfusion-spliced point. The pigtail optical fiber 181 and the opticalattenuating fiber 172 may be the same optical fiber. Therefore, aconfiguration without the third fusion-spliced point 174 c is possible.

It is preferable that a groove be provided to positions at the metalplate 173 where the optical receiving fiber 171 and the opticalattenuating fiber 172 are arranged, the optical receiving fiber 171 andthe optical attenuating fiber 172 be accommodated in the groove andfixed with a resin or the like. It is because it is possible to increasean effect of not only fixing the optical receiving fiber 171 and theoptical attenuating fiber 172 reliably but also conducting a thermalconversion, and exhausting a heat, of a leakage light of the returnlight leaking from the optical attenuating fiber 172 effectively. Themetal plate 173 serves as a thermal conversion portion converting lightcaused by a loss of the optical attenuating fiber 172 to heat.

It may be configured to monitor an intensity of the return light byarranging a light-receiving element or the like on the metal plate 173at a position where a leakage light of the return light may be received.For example, a stable measurement of the return light intensity ispossible by arranging the light-receiving element in vicinity A of thesecond fusion-spliced point 174 b or a portion of a bending portion towhich the return light is incident. Moreover, for example, alight-receiving element may be arranged in a vicinity B of the firstfusion-spliced point 174 a, and a light-receiving element may bearranged in a vicinity C surrounding the optical attenuating fiber 172or around the return-light-attenuating module 170.

It is preferable to provide a temperature sensor such as a thermistor orthe like to the metal plate 173. It is because a temperature of themetal plate 173 is correlated to an intensity of the return light and itmay be used to control etc. an output of the output laser light L whilemonitoring the intensity of the return light.

As illustrated in FIG. 28, it is preferable to cover thereturn-light-attenuating module 170 with a shielding plate. FIG. 28 is aside plan view of the return-light-attenuating module 170. Asillustrated in FIG. 28, a shielding plate 175 is arranged to be inapproximately parallel with the metal plate 173 by spacers 176. Theshielding plate 175 may be formed of the same material with the metalplate 173 or resin. An interval between the metal plate 173 and theshielding plate 175 is, for example, 6 mm, and the optical attenuatingfiber 172 is accommodated between the metal plate 173 and the shieldingplate 175.

By the above-described configuration, it is possible to restrain thereturn light leaking from the optical attenuating fiber 172 from beingemitted around the return-light-attenuating module 170. Since the returnlight leaking from the optical attenuating fiber 172 is confined withinthe return-light-attenuating module 170, a sensing accuracy for thereturn light when arranging the light-receiving element within thereturn-light-attenuating module 170 improves. This configuration obtainsan effect of being capable of increasing sensitivity of a temperaturesensor because a temperature gradient relative to an input powerincreases when arranging the light-receiving element within thereturn-light-attenuating module 170.

Herein an evaluation to a single unit of the return-light-attenuatingmodule 170 is explained while referring to FIGS. 29 and 30. FIG. 29 is agraph illustrating a temperature of an optical attenuating fiber 172relative to an input power to the return-light-attenuating module 170,and FIG. 30 is a graph illustrating an output power relative to theinput power to the return-light-attenuating module 170.

In the graph illustrated in FIG. 29, a vertical axis indicatestemperature [° C.], a horizontal axis indicates input power [W], andtemperatures of a second fusion-spliced point 174 b ((Point X)), anoptical attenuating fiber 172 (Point Y), and a metal plate 173 (Point Z)when inputting a wavelength of 1070 nm of laser light to a positioncorresponding to the first fusion-spliced point 174 a are plotted. Laserlights of a pedestal mode and a cladding mode are contained as well inthe laser light input to the position corresponding to the firstfusion-spliced point 174 a, and a ratio of the core mode is 70%. Sincethe temperature of the metal plate 173 follows, and varies in accordancewith, the temperatures of the second fusion-spliced point 174 b and theoptical attenuating fiber 172, the temperatures of the secondfusion-spliced point 174 b and the optical attenuating fiber 172 aremeasured by attaching a temperature sensor to the metal plate 173.

As illustrated in FIG. 29, the temperatures of the second fusion-splicedpoint 174 b, the optical attenuating fiber 172, and the metal plate 173show approximate linear characteristics relative to the input power tothe return-light-attenuating module 170. For example, relative to 600 Wof the input power as well, the second fusion-spliced point 174 b isequal to or less than 70° C., and the temperature of the metal plate 173is restrained at equal to or less than 60° C.

In the graph illustrated in FIG. 30, a left vertical axis indicatesoutput power [μW], a horizontal axis indicates input power [W], and aright vertical axis indicates attenuation amount indicated in decibel[dB], and an output power at a position corresponding to the thirdfusion-spliced point 174 c when inputting the wavelength of 1070 nm oflaser light to a position corresponding to the first fusion-splicedpoint 174 a is plotted. Similarly, the laser light input to the positioncorresponding to the first fusion-spliced point 174 a contains the laserlights of the pedestal mode and the cladding mode as well, and the ratioof the core mode is 70%.

As illustrated in FIG. 30, the return-light-attenuating module 170exerts an effect of attenuating approximately 58 dB relative to 0 W to600 W of input power, and the output power is restrained under 1 mWrelative to, for example, 600 W of input power as well.

As described above, in the optical fiber laser device 1300, thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber 172 of which bending loss relative in the return lightis greater than a bending loss in the visible light by a plurality ofrounds is connected to the first light-reflecting unit 112 via, forexample, the signal port optical fiber of the pumping-light multiplexer114, and the optical fiber laser device 1300 includes thevisible-light-emitting portion 180 into which the visible light isintroduced via the return-light-attenuating module 170. Therefore, theoptical fiber laser device 1300 described above is configured to be highin durability relative to the return light, and thus achieves highdurability and high output capability.

Fourteenth Embodiment

FIG. 31 illustrates a schematic configuration of an optical fiber laserdevice 1400 according to a fourteenth embodiment. As illustrated in FIG.31, the optical fiber laser device 1400 according to the fourteenthembodiment is an optical fiber laser type device generating output laserlight by using the laser oscillator 110. The laser oscillator 110 isprovided with the optical amplifying fiber 111 and is configured togenerate a laser resonance between the first light-reflecting unit 112and the second light-reflecting unit 113. The output laser lightgenerated by the laser oscillator 110 is irradiated as the output laserlight L to the workpiece W via the optical outputting fiber 120 and theirradiation head 121.

As illustrated in FIG. 31, the optical fiber laser device 1400 accordingto the fourteenth embodiment adopts the forward-pumping typeconfiguration. That is, in the optical fiber laser device 1400, pumpinglight is introduced in the forward direction of the laser oscillator110. For that purpose, the optical fiber laser device 1400 is providedwith the pumping-light multiplexer 114, at an upstream to the firstlight-reflecting unit 112, for introducing the pumping light to thelaser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the forward-direction-side signal port of thepumping-light multiplexer 114 is connected to the first light-reflectingunit 112. By this configuration, the pumping-light multiplexer 114multiplexes the pumping lights output by the pumping laser diodes 115 aand 115 b and outputs the pumping light to the laser oscillator 110. Thereturn-light-attenuating module 170 is connected to the signal portoptical fiber extending from the reverse-direction-side signal port ofthe pumping-light multiplexer 114. The configuration in thereturn-light-attenuating module 170 may be configured to be similar tothe first embodiment. The optical fiber laser device 1400 is providedwith the control unit 160 for controlling the pumping laser diodes 115 aand 115 b and other controlled sites.

In the optical fiber laser device 1400 according to the fourteenthembodiment, a terminal-treating portion 190 is provided at an end pointat the reverse direction side of the return-light-attenuating module170. The terminal-treating portion 190 is achieved by providing, forexample, a resin-sealing at a terminal of the optical fiber configuringthe return-light-attenuating module 170. Although the terminal-treatingportion 190 is described independently from the return-light-attenuatingmodule 170 in FIG. 31, the resin-sealing may be provided to the terminalof the optical fiber in the return-light-attenuating module 170.

FIG. 32 illustrates an example of the resin-sealing at the terminal ofthe optical fiber in the terminal-treating portion 190. As illustratedin FIG. 32, the terminal-treating portion 190 is provided with a sealingmember 191 sealing an end of the optical fiber. The sealing member 191is formed of a resin or the like and has characteristics of scatteringor absorbing the return light emitted from the end of the optical fiber.

A core 192 and a cladding 193 at the end of the optical fiber are cutobliquely relative to an optical axis of the optical fiber. It ispreferable to cut the end of the optical fiber obliquely in this mannerbecause an amount of light, among the return light, reflected at the endof the optical fiber and returning to the core decreases. When theintensity of the return light is low, the core 192 and the cladding 193at the end of the optical fiber may be cut vertically relative to theoptical axis of the optical fiber.

Although, a coating 194 is provided around the cladding 193 of theoptical fiber illustrated in FIG. 32, the coating 194 is not alwaysnecessary. It is possible to remove the coating 194 at the end portionor the entire of the optical fiber in consideration of affection by heatgenerated.

As described above, in the optical fiber laser device 1400, thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber whose bending loss in the return light is greater thana bending loss in the visible light by a plurality of rounds isconnected to the first light-reflecting unit 112 via the signal portoptical fiber of the pumping-light multiplexer 114, and the terminal ofthe return-light-attenuating module 170 is sealed with the resin.Therefore, the optical fiber laser device 1400 described above isconfigured to be high in durability relative to the return light, andthus achieves high durability and high output capability.

Fifteenth Embodiment

FIG. 33 illustrates a schematic configuration of an optical fiber laserdevice 1500 according to a fifteenth embodiment. As illustrated in FIG.33, the optical fiber laser device 1500 according to the thirdembodiment is an optical fiber laser type device generating output laserlight by using the laser oscillator 110. The laser oscillator 110includes the optical amplifying fiber 111 and is configured to generatea laser resonance between the first light-reflecting unit 112 and thesecond light-reflecting unit 113. The output laser light generated bythe laser oscillator 110 is irradiated as the output laser light L tothe workpiece W via the optical outputting fiber 120 and the irradiationhead 121.

As illustrated in FIG. 33, the optical fiber laser device 1500 accordingto the fifteenth embodiment adopts the forward-pumping typeconfiguration. That is, in the optical fiber laser device 1500, thepumping light is introduced in the forward direction of the laseroscillator 110. However, unlike the first embodiment, the optical fiberlaser device 1500 includes, between the first light-reflecting unit 112and the optical amplifying fiber 111, the pumping-light multiplexer 114for introducing the pumping light to the laser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the forward-direction-side signal port of thepumping-light multiplexer 114 is connected to the first light-reflectingunit 112. By this configuration, the pumping-light multiplexer 114multiplexes the pumping lights output by the pumping laser diodes 115 aand 115 b and outputs the pumping lights to the laser oscillator 110. Bythis configuration, the pumping-light multiplexer 114 multiplexes thepumping lights output by the pumping laser diodes 115 a and 115 b andoutputs the pumping lights to the laser oscillator 110. Thereverse-direction-side signal port of the pumping-light multiplexer 114is connected to the first light-reflecting unit 112. The optical fiberlaser device 1500 is provided with the pumping laser diodes 115 a and115 b and the control unit 160 for controlling other controlled sites.

The return-light-attenuating module 170 is connected to an optical fiberextending from the first light-reflecting unit 112. Unlike the firstembodiment, in the optical fiber laser device 1500 according to thefifteenth embodiment, the return-light-attenuating module 170 isconnected to the laser oscillator 110 not via the pumping-lightmultiplexer 114. However, the return-light-attenuating module 170 servessimilarly to the first embodiment in the fifteenth embodiment as well.The visible-light-emitting portion 180 introducing a visible light in aforward direction via the return-light-attenuating module 170 isconnected to the return-light-attenuating module 170.

As described above, in the optical fiber laser device 1500, thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber whose bending loss in the return light is greater thana bending loss in the visible light by a plurality of rounds isconnected to the first light-reflecting unit 112, and the optical fiberlaser device 1300 is provided with the visible-light-emitting portion180 into which the visible light is introduced via thereturn-light-attenuating module 170. Therefore, the optical fiber laserdevice 1500 described above is configured to be high in durabilityrelative to the return light, and thus achieves high durability and highoutput capability.

Sixteenth Embodiment

FIG. 34 illustrates a schematic configuration of an optical fiber laserdevice 1600 according to a sixteenth embodiment. As illustrated in FIG.34, the optical fiber laser device 1600 according to the sixteenthembodiment is an optical fiber laser type device generating laser lightby using the laser oscillator 110. The laser oscillator 110 is providedwith the optical amplifying fiber 111 and is configured to generate alaser resonance between the first light-reflecting unit 112 and thesecond light-reflecting unit 113. The laser light generated by the laseroscillator 110 is irradiated as the output laser light L to theworkpiece W via the optical outputting fiber 120 and the irradiationhead 121.

As illustrated in FIG. 34, the optical fiber laser device 1600 accordingto the sixteenth embodiment adopts the forward-pumping typeconfiguration. That is, in the optical fiber laser device 1600, pumpinglight is introduced in the forward direction of the laser oscillator110. For that purpose, the optical fiber laser device 1600 is providedwith the pumping-light multiplexer 114, at an upstream to the firstlight-reflecting unit 112, for introducing the pumping light to thelaser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the forward-direction-side signal port of thepumping-light multiplexer 114 is connected to the first light-reflectingunit 112. By this configuration, the pumping-light multiplexer 114multiplexes the pumping lights output by the pumping laser diodes 115 aand 115 b and outputs the pumping lights to the laser oscillator 110.The return-light-attenuating module 170 is connected to the signal portoptical fiber extending from the reverse-direction-side signal port ofthe pumping-light multiplexer 114. The optical fiber laser device 1600is provided with the control unit 160 for controlling the pumping laserdiodes 115 a and 115 b and other controlled sites.

In the optical fiber laser device 1600 according to the sixteenthembodiment, the optical sensor 136 is connected to an end point at thereverse direction side of the return-light-attenuating module 170. Theoptical sensor 136 makes light input via the return-light-attenuatingmodule 170 be subjected to photoelectric conversion, and measures anintensity of the return light transmitting through the firstlight-reflecting unit 112 of the laser oscillator 110. The intensity ofthe return light measured by the optical sensor 136 is transmitted tothe control unit 160. The intensity of the return light may be an indexfor determining as to whether or not the optical fiber laser device 1600is operated normally. On the other hand, the return light may be veryintense sometimes, and if it is input directly, the optical sensor 136may be damaged possibly. To address this, the optical fiber laser device1600 is configured to measure the intensity of the return lightattenuated by the return-light-attenuating module 170 appropriately.

As described above, in the optical fiber laser device 1600, thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber of which bending loss in the return light is greaterthan a bending loss in the visible light by a plurality of rounds isconnected to the first light-reflecting unit 112 via the signal portoptical fiber of the pumping-light multiplexer 114, and the opticalsensor 136 conducting photoelectric conversion is connected to aterminal of the return-light-attenuating module 170. Therefore, theoptical fiber laser device 1600 described above is configured to be highin durability relative to the return light, and thus achieves highdurability and high output capability.

Seventeenth Embodiment

FIG. 35 illustrates a schematic configuration of an optical fiber laserdevice 1700 according to a seventeenth embodiment. As illustrated inFIG. 35, the optical fiber laser device 1700 according to theseventeenth embodiment is an optical fiber laser type device generatingoutput laser light by using the laser oscillator 110. The laseroscillator 110 is provided with the optical amplifying fiber 111 and isconfigured to generate a laser resonance between the firstlight-reflecting unit 112 and the second light-reflecting unit 113. Theoutput laser light generated by the laser oscillator 110 is irradiatedas the output laser light L to the workpiece W via the opticaloutputting fiber 120 and the irradiation head 121.

As illustrated in FIG. 35, the optical fiber laser device 1700 accordingto the seventeenth embodiment adopts the forward-pumping typeconfiguration. That is, in the optical fiber laser device 1700, pumpinglight is introduced in the forward direction of the laser oscillator110. For that purpose, the optical fiber laser device 1700 is providedwith the pumping-light multiplexer 114, at an upstream to the firstlight-reflecting unit 112, for introducing the pumping light to thelaser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the forward-direction-side signal port of thepumping-light multiplexer 114 is connected to the first light-reflectingunit 112. By this configuration, the pumping-light multiplexer 114multiplexes the pumping lights output by the pumping laser diodes 115 aand 115 b and outputs the pumping lights to the laser oscillator 110.The optical fiber laser device 1700 is provided with the control unit160 for controlling the pumping laser diodes 115 a and 115 b and othercontrolled sites.

In the optical fiber laser device 1700 according to the seventeenthembodiment, the return-light-attenuating module 170 is connected to adownstream, split by an optical multiplexer/demultiplexer 1706, to thesignal port optical fiber extending from the reverse-direction-sidesignal port of the pumping-light multiplexer 114. One, for example,called a Tap coupler or a wavelength division multiplex opticalmultiplexer/demultiplexer or the like may be used for the opticalmultiplexer/demultiplexer 1706. The Tap coupler demultiplexes an inputlight by a predetermined intensity ratio without wavelength dependency,and the wavelength division multiplex optical multiplexer/demultiplexeris capable of demultiplexing an input light by a predetermined intensityratio while having a wavelength dependency. Therefore, the return lightafter being attenuated by the optical multiplexer/demultiplexer 1706 issupposed to be input to the return-light-attenuating module 170. Thevisible-light-emitting portion 180 introducing a visible light in aforward direction via the return-light-attenuating module 170 isconnected to the return-light-attenuating module 170.

As described above, in the optical fiber laser device 1700, thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber of which bending loss in the return light is greaterthan a bending loss in the visible light by a plurality of rounds isconnected to the first light-reflecting unit 112 via the signal portoptical fiber of the pumping-light multiplexer 114, and the opticalfiber laser device 1700 is provided with the visible-light-emittingportion 180 into which the visible light is introduced via thereturn-light-attenuating module 170. Therefore, the optical fiber laserdevice 1700 described above is configured to be high in durabilityrelative to the return light, and thus achieves high durability and highoutput capability.

Eighteenth Embodiment

FIG. 36 illustrates a schematic configuration of an optical fiber laserdevice 1800 according to the eighteenth embodiment. As illustrated inFIG. 36, the optical fiber laser device 1800 according to the eighteenthembodiment is an optical fiber laser type device generating laser lightby using the laser oscillator 110. The laser oscillator 110 is providedwith the optical amplifying fiber 111 and is configured to generate alaser resonance between the first light-reflecting unit 112 and thesecond light-reflecting unit 113. The output laser light generated bythe laser oscillator 110 is irradiated as the output laser light L tothe workpiece W via the optical outputting fiber 120 and the irradiationhead 121.

As illustrated in FIG. 36, the optical fiber laser device 1800 accordingto the eighteenth embodiment adopts the forward-pumping typeconfiguration. That is, in the optical fiber laser device 1800, pumpinglight is introduced in the forward direction of the laser oscillator110. For that purpose, the optical fiber laser device 1800 is providedwith the pumping-light multiplexer 114, at an upstream to the firstlight-reflecting unit 112, for introducing the pumping light to thelaser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the forward-direction-side signal port of thepumping-light multiplexer 114 is connected to the first light-reflectingunit 112. By this configuration, the pumping-light multiplexer 114multiplexes the pumping lights output by the pumping laser diodes 115 aand 115 b and outputs the pumping lights to the laser oscillator 110.The optical fiber laser device 1800 is provided with the control unit160 for controlling the pumping laser diodes 115 a and 115 b and othercontrolled sites.

In the optical fiber laser device 1800 according to the eighteenthembodiment, the return-light-attenuating module 170 is connected to aport, among the light-pumping port of the pumping-light multiplexer 114,to which the pumping laser diodes 115 a and 115 b are not connected (aso-called redundant port), and is configured so that the attenuatedreturn light is irradiated from an end portion on the opposite side tothe optical outputting fiber 120 (an end portion from which the returnlight is emitted). A multi-mode optical fiber extends to thelight-pumping port of the pumping-light multiplexer 114. For example,for this multi-mode optical fiber, NA is 0.22, a core diameter is 110μm, and a cladding diameter is 125 μm. Therefore, it is preferable thata same kind of multi-mode optical fiber be selected as an opticalreceiving fiber of the return-light-attenuating module 170 so that aconnection loss decreases when the optical receiving fiber is connectedto this multi-mode optical fiber. Although an inner configuration of thereturn-light-attenuating module 170 may be similar to the firstembodiment, the optical attenuating fiber 172 may be the multi-modeoptical fiber. The visible-light-emitting portion 180 introducing avisible light in a forward direction via the return-light-attenuatingmodule 170 is connected to the return-light-attenuating module 170.

As described above, in the optical fiber laser device 1800, thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber of which bending loss in the return light is greaterthan a bending loss in the visible light by a plurality of rounds isconnected to the first light-reflecting unit 112 via the signal portoptical fiber of the pumping-light multiplexer 114, and the opticalfiber laser device 1700 is provided with the visible-light-emittingportion 180 into which the visible light is introduced via thereturn-light-attenuating module 170. Therefore, the optical fiber laserdevice 1800 described above is configured to be high in durabilityrelative to the return light, and thus achieves high durability and highoutput capability.

Nineteenth Embodiment

FIG. 37 illustrates a schematic configuration of an optical fiber laserdevice 1900 according to a nineteenth embodiment. As illustrated in FIG.37, the optical fiber laser device 1900 according to the nineteenthembodiment is an optical fiber laser type device generating laser lightby using the laser oscillator 110. The laser oscillator 110 is providedwith the optical amplifying fiber 111 and is configured to generate alaser resonance between the first light-reflecting unit 112 and thesecond light-reflecting unit 113. The output laser light generated bythe laser oscillator 110 is irradiated as the output laser light L tothe workpiece W via the optical outputting fiber 120 and the irradiationhead 121.

As illustrated in FIG. 37, the optical fiber laser device 1900 accordingto the nineteenth embodiment adopts a so-called backward-pumpingconfiguration. That is, in the optical fiber laser device 1900, pumpinglight is introduced in a backward direction of the laser oscillator 110.For that purpose, the optical fiber laser device 1900 is provided withthe pumping-light multiplexer 114, at a downstream to the secondlight-reflecting unit 113, for introducing the pumping light to thelaser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the reverse-direction-side signal port of thepumping-light multiplexer 114 is connected to the secondlight-reflecting unit 113. By this configuration, the pumping-lightmultiplexer 114 multiplexes the pumping lights output by the pumpinglaser diodes 115 a and 115 b and outputs the pumping lights to the laseroscillator 110. The optical fiber laser device 1900 is provided with thecontrol unit 160 for controlling the pumping laser diodes 115 a and 115b and other controlled sites.

In the optical fiber laser device 1900 according to the nineteenthembodiment, the return-light-attenuating module 170 is connected to aport, among the light-pumping port of the pumping-light multiplexer 114,to which the pumping laser diodes 115 a and 115 b are not connected (aso-called redundant port), and is configured so that the attenuatedreturn light is irradiated from an end portion on the opposite side tothe optical outputting fiber 120 (an end portion from which the returnlight is emitted). A multi-mode optical fiber extends to thelight-pumping port of the pumping-light multiplexer 114, and it ispreferable that an optical receiving fiber of thereturn-light-attenuating module 170 be selected so that a connectionloss decreases when the optical receiving fiber is connected to thismulti-mode optical fiber. The visible-light-emitting portion 180introducing a visible light in a forward direction via thereturn-light-attenuating module 170 is connected to thereturn-light-attenuating module 170.

As described above, in the optical fiber laser device 1900, thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber of which bending loss in the return light is greaterthan a bending loss in the visible light by a plurality of rounds isconnected to the second light-reflecting unit 113 via the signal portoptical fiber of the pumping-light multiplexer 114, and the opticalfiber laser device 1700 is provided with the visible-light-emittingportion 180 into which the visible light is introduced via thereturn-light-attenuating module 170. Therefore, the optical fiber laserdevice 1900 described above is configured to be high in durabilityrelative to the return light, and thus achieves high durability and highoutput capability.

Twentieth Embodiment

FIG. 38 illustrates a schematic configuration of an optical fiber laserdevice 2000 according to a twentieth embodiment. As illustrated in FIG.38, the optical fiber laser device 2000 according to the twentiethembodiment is a so-called master oscillator power-amplifier structure ofan optical fiber laser type device generating output laser light byusing the laser oscillator 110 and amplifying the output laser lightgenerated by the laser oscillator 110 with an amplifier 110 a. The laseroscillator 110 is provided with the optical amplifying fiber 111 and isconfigured to generate a laser resonance between the firstlight-reflecting unit 112 and the second light-reflecting unit 113. Theoutput laser light generated by the laser oscillator 110 is amplifiedwhile propagating through the optical amplifying fiber 716 of theamplifier 110 a and irradiated as the output laser light L to theworkpiece W via the optical outputting fiber 120 and the irradiationhead 121.

As illustrated in FIG. 38, any one of the laser oscillator 110 and theamplifier 110 a of the optical fiber laser device 2000 according to thetwentieth embodiment adopts the forward-pumping type configuration. Thatis, in the optical fiber laser device 2000, pumping light is introducedin the forward direction of the laser oscillator 110 and the amplifier110 a. For that purpose, the optical fiber laser device 2000 is providedwith the pumping-light multiplexer 114, at an upstream to the firstlight-reflecting unit 112, for introducing the pumping light to thelaser oscillator 110, and is provided with the second pumping-lightmultiplexer 717, between the second light-reflecting unit 113 and theoptical amplifying fiber 716, for introducing the pumping light to theamplifier 110 a.

The first pumping-light multiplexer 114 and the second pumping-lightmultiplexer 717 are configured by, for example, TFBs similarly to thefirst embodiment. The light-pumping port of the first pumping-lightmultiplexer 114 is connected to the pumping laser diodes 115 a and 115b, and the forward-direction-side signal port of the first pumping-lightmultiplexer 114 is connected to the first light-reflecting unit 112. Bythis configuration, the pumping-light multiplexer 114 multiplexes thepumping lights output by the pumping laser diodes 115 a and 115 b andoutputs the pumping lights to the laser oscillator 110. On the otherhand, the light-pumping port of the second pumping-light multiplexer 717is connected to the pumping laser diodes 718 a and 718 b, thereverse-direction-side signal port of the second pumping-lightmultiplexer 717 is connected to the second light-reflecting unit 113,and the reverse-direction-side signal port of the second pumping-lightmultiplexer 717 is connected to the optical amplifying fiber 716. Bythis configuration, the second pumping-light multiplexer 717 multiplexesthe pumping lights output by pumping laser diodes 118 a and 118 b andoutputs the pumping lights to the amplifier 110 a.

The return-light-attenuating module 170 is connected to a signal portoptical fiber extending from the reverse-direction-side signal port ofthe first pumping-light multiplexer 114. The inner configuration of thereturn-light-attenuating module 170 may be similar to the firstembodiment. The visible-light-emitting portion 180 introducing a visiblelight in a forward direction via the return-light-attenuating module 170is connected to the return-light-attenuating module 170. The opticalfiber laser device 2000 is provided with the control unit 160 forcontrolling the pumping laser diodes 115 a, 115 b, 718 a, 718 b,visible-light-emitting portion 180, and the other controlled sites.

As described above, in the optical fiber laser device 2000, thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber of which bending loss in the return light is greaterthan a bending loss in the visible light by a plurality of rounds isconnected to the second light-reflecting unit 113 via the signal portoptical fiber of the pumping-light multiplexer 114, and the opticalfiber laser device 2000 is provided with the visible-light-emittingportion 180 into which the visible light is introduced via thereturn-light-attenuating module 170. Therefore, the optical fiber laserdevice 2000 described above is configured to be high in durabilityrelative to the return light, and thus achieves high durability and highoutput capability.

Twenty-First Embodiment

FIG. 39 illustrates a schematic configuration of an optical fiber laserdevice 2100 according to a twenty-first embodiment. As illustrated inFIG. 39, the optical fiber laser device 2100 according to thetwenty-first embodiment is an optical fiber laser type device generatinglaser light by using the laser oscillator 110. The laser oscillator 110is provided with the optical amplifying fiber 111 and is configured togenerate a laser resonance between the first light-reflecting unit 112and the second light-reflecting unit 113. The output laser lightgenerated by the laser oscillator 110 is irradiated as the output laserlight L to the workpiece W via the optical outputting fiber 120 and theirradiation head 121.

As illustrated in FIG. 39, the optical fiber laser device 2100 accordingto the twenty-first embodiment adopts the forward-pumping typeconfiguration. That is, in the optical fiber laser device 2100, pumpinglight is introduced in the forward direction of the laser oscillator110. For that purpose, the optical fiber laser device 2100 is providedwith the pumping-light multiplexer 114, at an upstream to the firstlight-reflecting unit 112, for introducing the pumping light to thelaser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the forward-direction-side signal port of thepumping-light multiplexer 114 is connected to the first light-reflectingunit 112. By this configuration, the pumping-light multiplexer 114multiplexes the pumping lights output by the pumping laser diodes 115 aand 115 b and outputs the pumping light to the laser oscillator 110. Theoptical fiber laser device 2100 is provided with the control unit 160for controlling the pumping laser diodes 115 a and 115 b and othercontrolled sites.

In the optical fiber laser device 2100 according to the twenty-firstembodiment, an optical multiplexer/demultiplexer 2101 is provided in themiddle of the optical outputting fiber 120, and thereturn-light-attenuating module 170 is connected to an optical fiber, atan reverse direction side, of optical fibers split by the opticalmultiplexer/demultiplexer 2101, and it is configured so that theattenuated return light is emitted from an end portion on an oppositeside of the optical outputting fiber 120 (an end portion emitting thereturn light). One, for example, called a Tap coupler or a wavelengthdivision multiplex optical multiplexer/demultiplexer or the like may beused for the optical multiplexer/demultiplexer 2101, and any one ofthose has light-splitting characteristics of attenuating the returnlight splitting from the optical multiplexer/demultiplexer 2101 andinput to the return-light-attenuating module 170 and outputting thevisible light output from the visible-light-emitting portion 180 fromthe optical fiber laser device 2100 with a visible intensity. The innerconfiguration of the return-light-attenuating module 170 may be similarto the first embodiment. The visible-light-emitting portion 180introducing a visible light in a forward direction via thereturn-light-attenuating module 170 is connected to thereturn-light-attenuating module 170. The visible light emitted by thevisible-light-emitting portion 180 may be used for a guide light by theabove-described configuration as well.

As described above, the optical fiber laser device 2100 includes thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber, of which bending loss in the return light is greaterthan a bending loss in the visible light by a plurality of rounds, andthe visible-light-emitting portion 180 into which the visible light isintroduced via the return-light-attenuating module 170. Therefore, theoptical fiber laser device 2100 described above is configured to be highin durability relative to the return light, and thus achieves highdurability and high output capability.

Twenty-Second Embodiment

FIG. 40 illustrates a schematic configuration of an optical fiber laserdevice 2200 according to a twenty-second embodiment. As illustrated inFIG. 40, the optical fiber laser device 2200 according to thetwenty-second embodiment is an optical fiber laser type devicegenerating output laser light by using the laser oscillator 110. Thelaser oscillator 110 is provided with the optical amplifying fiber 111and is configured to generate a laser resonance between the firstlight-reflecting unit 112 and the second light-reflecting unit 113. Theoutput laser light generated by the laser oscillator 110 is irradiatedas the output laser light L to the workpiece W via the opticaloutputting fiber 120 and the irradiation head 121.

As illustrated in FIG. 40, the optical fiber laser device 2200 accordingto the twenty-second embodiment adopts the forward-pumping typeconfiguration. That is, in the optical fiber laser device 2200, pumpinglight is introduced in the forward direction of the laser oscillator110. For that purpose, the optical fiber laser device 2200 is providedwith the pumping-light multiplexer 114, at an upstream to the firstlight-reflecting unit 112, for introducing the pumping light to thelaser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the forward-direction-side signal port of thepumping-light multiplexer 114 is connected to the first light-reflectingunit 112. By this configuration, the pumping-light multiplexer 114multiplexes the pumping lights output by the pumping laser diodes 115 aand 115 b and outputs the pumping light to the laser oscillator 110. Theoptical fiber laser device 2200 is provided with the control unit 160for controlling the pumping laser diodes 115 a and 115 b and othercontrolled sites.

In the optical fiber laser device 2200 according to the twenty-secondembodiment, an optical multiplexer/demultiplexer 2201 is provided in themiddle of the optical outputting fiber 120, and thereturn-light-attenuating module 170 is connected to an optical fiber, ata forward direction side, of optical fibers split by the opticalmultiplexer/demultiplexer 2101. One, for example, called a Tap coupleror a wavelength division multiplex optical multiplexer/demultiplexer orthe like may be used for the optical multiplexer/demultiplexer 2201. Theinner configuration of the return-light-attenuating module 170 may besimilar to the first embodiment. The visible-light-emitting portion 180introducing a visible light in a forward direction via thereturn-light-attenuating module 170 is connected to thereturn-light-attenuating module 170.

By the above-described configuration, the visible light emitted by thevisible-light-emitting portion 180 may be used for failure analysis.That is, when a failure like disconnection or the like is considered tooccur on the optical path such as, for example, the optical outputtingfiber 120, the optical amplifying fiber 111, and the like, for theoutput laser light in the optical fiber laser device 2200, the controlunit 160 makes the visible-light-emitting portion 180 emit light in astate of stopping operations of the pumping laser diodes 115 a and 115b. The visible light emitted from the visible-light-emitting portion 180is propagated through the optical outputting fiber 120, the opticalamplifying fiber 111, and the like, in this order. If it is assumed thatthere is disconnection on the optical path, since the visible lightleaks to outside at a point of the disconnection, the point ofdisconnection may be identified visually.

As described above, the optical fiber laser device 2200 includes thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber, of which bending loss in the return light is greaterthan a bending loss in the visible light by a plurality of rounds, andthe visible-light-emitting portion 180 into which the visible light isintroduced via the return-light-attenuating module 170. Therefore, theoptical fiber laser device 2200 described above is configured to be highin durability relative to the return light, and thus achieves highdurability and high output capability.

Twenty-Third Embodiment

FIG. 41 illustrates a schematic configuration of an optical fiber laserdevice 2300 according to the twenty-third embodiment. As illustrated inFIG. 41, the optical fiber laser device 2300 according to thetwenty-third embodiment includes a plurality of optical fiber laserportions 23001, . . . , 2300 n-1, and 2300 n, the output laser lightsoutput by the respective optical fiber laser portions 23001, . . . ,2300 n-1, and 2300 n are coupled at a combiner 2301 and irradiated asthe output laser light L to the workpiece W via the optical outputtingfiber 120 and the irradiation head 121.

Each of the optical fiber laser portions 23001, . . . , 2300 n-1, and2300 n is an independent virtual optical fiber laser device. Therefore,hereafter only a configuration of the optical fiber laser portion 23001will be explained as a representative.

The optical fiber laser portion 23001 is an optical fiber laser typedevice generating output laser light by using the laser oscillator 110.The laser oscillator 110 is provided with the optical amplifying fiber111 and is configured to generate a laser resonance between the firstlight-reflecting unit 112 and the second light-reflecting unit 113.

As illustrated in FIG. 41, the optical fiber laser portion 23001 adoptsthe forward-pumping type configuration. That is, in the optical fiberlaser portion 23001, pumping light is introduced in the forwarddirection of the laser oscillator 110. For that purpose, the opticalfiber laser portion 23001 is provided with the pumping-light multiplexer114, at an upstream to the first light-reflecting unit 112, forintroducing the pumping light to the laser oscillator 110.

The pumping-light multiplexer 114 is configured by, for example, the TFBsimilarly to the first embodiment. The light-pumping port of thepumping-light multiplexer 114 is connected to the pumping laser diodes115 a and 115 b, and the forward-direction-side signal port of thepumping-light multiplexer 114 is connected to the first light-reflectingunit 112. By this configuration, the pumping-light multiplexer 114multiplexes the pumping lights output by the pumping laser diodes 115 aand 115 b and outputs the pumping light to the laser oscillator 110.

In the optical fiber laser device 2300 according to the twenty-thirdembodiment, the return-light-attenuating module 170 is connected to aport, among ports of the combiner 2301, to which optical fiber laserportions 11001, . . . , 1100 n-1, and 1100 n are not connected, and isconfigured so that the attenuated return light is irradiated from an endportion on the opposite side to the optical outputting fiber 120 (an endportion from which the return light is emitted). Moreover, thevisible-light-emitting portion 180 introducing a visible light in aforward direction via the return-light-attenuating module 170 isconnected to the return-light-attenuating module 170. The visible lightemitted by the visible-light-emitting portion 180 may be used for aguide light by the above-described configuration as well.

As described above, the optical fiber laser device 2300 includes thereturn-light-attenuating module 170 configured by bending the opticalattenuating fiber, of which bending loss in the return light is greaterthan a bending loss in the visible light by a plurality of rounds, andthe visible-light-emitting portion 180 into which the visible light isintroduced via the return-light-attenuating module 170. Therefore, theabove-described optical fiber laser device 2300 is configured to be highin durability relative to the return light, and thus achieves highdurability and high output capability.

The present disclosure having been described based the embodiments isnot limited to the above-described embodiments. The present disclosureincludes a configuration combining components of each of theabove-described embodiments. The present disclosure includes all ofother embodiments, examples, operation techniques, and the like carriedout based on the above-described embodiments by an ordinary skilledperson in the art.

For example, although the above-described embodiments were describedbased on configuration examples of the forward-pumping laser oscillatorand amplifier, the present disclosure may be carried out appropriatelyeven by the backward-pumping laser oscillator and amplifier, and even bythe bidirectional pumping laser oscillator and amplifier pumping in boththe forward direction and the backward direction. Although only oneembodiment configured to include the amplifier was explained in theabove-described embodiments, it is possible to configure each embodimentto add an amplifier.

Although the return-light-attenuating module is provided at one locationin each of the above-described embodiments, it goes without saying thata plurality of optical attenuation modules may be provided to oneoptical fiber laser device. A configuration of providing a plurality ofoptical attenuation modules to one port may be included in the scope ofthe present disclosure. The number of composing parts connected to onereturn-light-attenuating module is not limited to one, and an opticalfiber may be split by an optical multiplexer/demultiplexer to beconnected to, for example, a plurality of visible-light emitting unit, adetector and the like.

The visible light emitted by the visible-light emitting unit is notlimited to red in color (wavelength of 660 nm), and a more visible greenlight may be used. It may be configured that a wavelength-dependencyelement is provided inside the visible-light emitting unit to limit awavelength of the return light. Moreover, a space-coupling type shuttermay be introduced to the visible-light-emitting unit to close theshutter when oscillating output laser light.

The present disclosure has been made in view of the above and an objectof the present disclosure is to provide an optical fiber laser devicehaving high durability and high output capability.

Although the disclosure has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

What is claimed is:
 1. An optical fiber laser device for generatinglaser light by using an optical amplifying fiber as an amplificationmedium in a laser oscillator, the optical fiber laser device comprising:an optical outputting fiber configured to emit laser light to anoutside; a return-light-attenuating portion configured to attenuatereturn light propagating through at least the optical outputting fiberin a reverse direction of the laser light; a thermal conversion unitprovided at the return-light-attenuating portion and configured toconvert the return light into heat; a temperature-monitoring deviceconfigured to measure an increase in a temperature, of thereturn-light-attenuating portion, caused by the heat converted by thethermal conversion unit; and a control unit configured to decrease orstop an output of the laser light when the temperature measured by thetemperature-monitoring device becomes a predetermined thresholdtemperature or higher.
 2. The optical fiber laser device according toclaim 1, wherein the temperature-monitoring device measures atemperature difference between temperatures at a first temperaturemeasurement point where the heat converted by the thermal conversionunit is measured via a thermal conductor and at a second temperaturemeasurement point which is a reference point for measuring a temperatureof the optical fiber laser device.
 3. The optical fiber laser deviceaccording to claim 1, wherein the thermal conversion unit is configuredwith an axis-offset-fusion-splice of optical fibers at thereturn-light-attenuating portion.
 4. The optical fiber laser deviceaccording to claim 1, wherein the thermal conversion unit is formed of ahigh loss optical fiber provided at the return-light-attenuatingportion.
 5. The optical fiber laser device according to claim 1, whereinthe thermal conversion unit is formed of an intentionally coiled opticalfiber provided at the return-light-attenuating portion.
 6. The opticalfiber laser device according to claim 1, wherein the thermal conversionunit is formed of a resin sealing an end of the optical fiber providedat the return-light-attenuating portion.
 7. The optical fiber laserdevice according to claim 1, wherein the thermal conversion unit isformed of an irradiation surface of the thermal conductor to which thereturn light emitted from the end of the optical fiber provided at thereturn-light-attenuating portion is irradiated.
 8. The optical fiberlaser device according to claim 1, wherein the return-light-attenuatingportion is disposed at an upstream side of the laser oscillator in adirection of a laser propagation.
 9. The optical fiber laser deviceaccording to claim 8, further comprising a pumping-light multiplexerincluding an output-side signal port, an input-side signal port, and aplurality of pumping-light ports, wherein the pumping-light multiplexeris configured to output pumping light input from the pumping-light portsvia the output-side signal port connected to the laser oscillator, andthe return-light-attenuating portion is provided at a terminal portionof an optical fiber connected to the input-side signal port of thepumping-light multiplexer.
 10. The optical fiber laser device accordingto claim 8, further comprising a pumping-light multiplexer including anoutput-side signal port, an input-side signal port, and a plurality ofpumping-light ports, wherein the pumping-light multiplexer is configuredto output pumping light input from the pumping-light ports via theoutput-side signal port connected to the laser oscillator, and thereturn-light-attenuating portion is provided at a terminal portion of anoptical fiber connected to the pumping-light port of the pumping-lightmultiplexer.
 11. The optical fiber laser device according to claim 10,wherein the return-light-attenuating portion is provided at the terminalportion of the optical fiber connected to one of the pumping-light portsat which an intensity of the return light is maximum out of thepumping-light ports to which a light source outputting the pumping lightis not connected.
 12. The optical fiber laser device according to claim8, wherein the return-light-attenuating portion is provided at aterminal portion of an optical fiber connected to one whose reflectivityrelative to the laser light is higher than the other out of twolight-reflecting units configuring the laser oscillator.
 13. The opticalfiber laser device according to claim 1, further comprising: an opticalamplifier provided between the laser oscillator and the opticaloutputting fiber and formed by using an optical amplifying fiber as anamplification medium; and a second pumping-light multiplexer includingan output-side signal port, an input-side signal port, and a pluralityof pumping-light ports and configured to output pumping light input fromthe pumping-light port via the output-side signal port connected to theoptical amplifier to introduce the pumping light to the opticalamplifying fiber included in the optical amplifier, wherein thereturn-light-attenuating portion is provided at a terminal portion of anoptical fiber connected to the pumping-light port of the secondpumping-light multiplexer.
 14. An optical fiber laser device forgenerating laser light by using an optical amplifying fiber as anamplification medium in a laser oscillator, the optical fiber laserdevice comprising: an optical outputting fiber configured to outputlaser light to an outside in a forward direction; and areturn-light-attenuating portion formed of an optical attenuating fibercoiled for a plurality of rounds, wherein a bending loss in return lightis greater than a bending loss in visible light, the return light beinginfrared light propagating through the optical outputting fiber in areverse direction of the laser light.
 15. The optical fiber laser deviceaccording to claim 14, wherein the return-light-attenuating portion isconnected to an optical fiber disposed at an upstream side relative to areflection unit, of the laser oscillator, having high reflectivity. 16.The optical fiber laser device according to claim 15, wherein thereturn-light-attenuating portion is connected to an optical fiber at areverse direction side relative to the reflection unit via a signal portoptical fiber of a pumping-light multiplexer for introducing pumpinglight used for laser oscillation of the laser oscillator to the opticalamplifying fiber.
 17. The optical fiber laser device according to claim15, wherein the return-light-attenuating portion is connected to anoptical fiber at a reverse direction side relative to the reflectionunit via a pumping light port of the pumping-light multiplexer forintroducing pumping light used for laser oscillation of the laseroscillator to the optical amplifying fiber.
 18. The optical fiber laserdevice according to claim 14, wherein the return-light-attenuatingportion is connected to an optical fiber split from an opticalmultiplexer/demultiplexer provided in a middle of the optical outputtingfiber.
 19. The optical fiber laser device according to claim 14, furthercomprising a visible-light-emitting portion introducing the visiblelight to the optical outputting fiber via the return-light-attenuatingportion.
 20. The optical fiber laser device according to claim 19,wherein a bend edge wavelength of the optical attenuating fiber isshorter than a wavelength of the return light.
 21. The optical fiberlaser device according to claim 19, wherein the optical attenuatingfiber is configured to propagate the visible light in a substantiallysingle mode.
 22. The optical fiber laser device according to claim 21,wherein the optical attenuating fiber is configured to propagate ared-color light in a substantially single mode.
 23. The optical fiberlaser device according to claim 14, wherein a terminal of thereturn-light-attenuating portion is sealed by a resin.
 24. The opticalfiber laser device according to claim 14, wherein an optical sensorconducting a photoelectric conversion is connected to a terminal of thereturn-light-attenuating portion.
 25. An optical fiber laser device forgenerating laser light by using an optical amplifying fiber as anamplification medium in a laser oscillator, the optical fiber laserdevice comprising: an optical outputting fiber configured to output thelaser light to an outside in a forward direction; and areturn-light-attenuating portion configured to attenuate an opticalintensity of return light including infrared light propagating a core ofthe optical outputting fiber in a reverse direction and emit theattenuated return light from an end portion on an opposite side to theoptical outputting fiber, wherein the return-light-attenuating portionincludes: a return light propagation loss portion made of a medium, themedium giving a loss to the return light continuously in a direction ofpropagation of the return light; and a thermal conversion portionconfigured to convert light generated by the loss into heat, a majorportion of the return light is attenuated and subjected to thermalconversion at the return light propagation loss portion, and onlyresidual light, of which intensity is minute, after being attenuated isoutput from an end portion of the return light propagation loss portion.26. The optical fiber laser device according to claim 25, wherein thereturn light propagation loss portion is an optical fiber including acore connected to a core of an optical fiber included in the laseroscillator of the optical fiber laser device, and the major portion ofthe return light is attenuated at the core included in the return lightpropagation loss portion.
 27. The optical fiber laser device accordingto claim 26, wherein a loss, of the core of the optical fiber includedin the return light propagation loss portion, at a wavelength of aninfrared laser light output from the optical outputting fiber is greaterthan a loss at a visible wavelength bandwidth.
 28. The optical fiberlaser device according to claim 27, wherein the core of the opticalfiber included in the return light propagation loss portion has singlemode propagation characteristics at the visible wavelength bandwidth.29. The optical fiber laser device according to claim 25, furthercomprising a visible-light-emitting portion configured to introduce thevisible light to the optical outputting fiber via thereturn-light-attenuating portion.
 30. The optical fiber laser deviceaccording to claim 25, wherein an optical sensor conducting aphotoelectric conversion is connected to a terminal of thereturn-light-attenuating portion.